WHOEVER WAS TRYING TO REACH ME hung up after only two rings. But I managed to catch the 301 area code on my caller-ID screen and thought, "Carlos."

Carlos was a source I'd known for almost four years. His specialty was analyzing videotapes made during the infamous 1993 Waco siege. For months he'd been calling me every week, but I hadn't heard from him lately. I dialed his office number.

A strange voice answered. That had never happened before.

"Is Carlos there?" I asked.

"Uh, he's not . . . umm . . . available right now," the guy on the other end mumbled.

"Who is this?" I said.

The voice identified himself as a police sergeant. I said I was a reporter and he signed off abruptly: "I can't discuss anything with you right now."

Had I had dialed into a crime scene? It figured. Things were always weird with Waco. After all these years, the surprises--and the mysteries--never seemed to end.

"Give Carlos the message that I called," I told the sergeant.

Carlos Ghigliotti would never get that message. He was, at that moment, deceased. The police had just discovered his corpse in an advanced state of decomposition at the office where he worked alone--Infrared Technologies Corp., on the third floor of a former bank building in downtown Laurel.

It was the afternoon of April 28. A seemingly healthy man was dead at 42. Nobody had seen him in weeks; nobody had reported him missing. Police found no sign of suicide or a break-in. Citing the unusual circumstances of his death, they were investigating it as a possible homicide.

Soon my phone was burning up with calls from people who knew of Ghigliotti's work on Waco and had heard he was dead. Maybe he was poisoned, some suggested, just as he was preparing to expose the whole sordid coverup.

The Internet boiled over with conspiracy theories. "Carlos Ghigliotti," stated one typical message, "was a man who knew too much." On Web sites like www.freerepublic.com, his name was put on lists with others who had allegedly perished from "Arkancide"--that's what the paranoiacs called other untimely deaths they'd somehow linked to the Clinton administration.

Ghigliotti, an expert in thermal imaging, was retained by the House Government Reform Committee last year to probe allegations that FBI agents--despite their vehement assertions to the contrary--had fired their weapons at members of the Branch Davidian sect, trapping helpless women and children inside the burning compound on April 19, 1993. Last fall I had quoted him in The Post as saying that infrared surveillance tapes--as well as regular videos made by the media--contained proof that the FBI fired: "The gunfire . . . is there, without a doubt."

In March he was finalizing his report to Congress, and he also had been advising attorneys waging a $100 million wrongful death suit against the government on behalf of the Davidians and their heirs. "I still have a lot of shocking evidence to show you," he wrote in a March 28 letter to Michael Caddell, the lead attorney in that case.

When his body was discovered, Ghigliotti's office got the scrutiny that Vince Foster's warranted after his suicide. Police sealed the premises and carted off computers and files. Rep. Dan Burton (R-Ind.), whose committee had retained Ghigliotti, called for "a full and thorough investigation." The Justice Department's special counsel on Waco, John C. Danforth, asked a federal court to take control of all evidence from Ghigliotti's firm.

I'd spent hours in that workshop, reviewing tapes on his eight-monitor JVC video console, looking for evidence of government perfidy in grainy images, debating theories while his beloved cats, Simone and Sipowicz, lolled at our feet. Carlos could be exasperating--brusque, inflexible and short-tempered, a fireplug of a guy who carried himself like a street fighter--but he had a soft side. More than once he admitted to breaking down in tears while examining Waco evidence. Someone had to speak for the dead, he told me. He believed with all his heart that he had finally uncovered the Truth.

"I've solved the case," he announced during one of his calls in March, urging me to come once again to his lab to review videotapes. "I know exactly what happened."

But I was busy on other stories and never made it back. Now there was one more mystery to unravel: Was Carlos the final victim of Waco?

Theorists and Theories

In the summer of 1996, a private investigator named Gordon Novel--a thin, bearded, tightly wound character who'd been enmeshed in conspiracy investigations since the JFK assassination--brought a piece of surveillance tape to Ghigliotti's office for examination. The black-and-white video was recorded by the FBI's Night Stalker plane as it circled lazily over the Branch Davidian compound, using a technology known as Forward Looking Infrared. (FLIR--pronounced fleer--detects temperature differences; heat sources register brightly on videotape.)

The Waco FLIR has become a Rosetta Stone for researchers because it shows what the media's cameras--set up miles away--couldn't see that day. It recorded the action at the back of the compound, as tanks smashed down walls and dismantled the building. A portion of the tape was filed in court in 1994 when federal prosecutors put the surviving followers of David Koresh on trial.

Seventy-five sect members died in the Waco inferno. President Clinton called it a typical cult suicide, but the Davidians said the havoc and rubble created by the tanks--not to mention clouds of tear gas--prevented many from fleeing the church. Scrutinizing the tape, Novel and others also noticed strange, repetitive flashes emanating from positions near the tanks. They claimed these were the thermal signatures of gunfire, but officials from Attorney General Janet Reno on down swore the FBI never fired that day. Government spokesmen said the flashes were nothing more than glints of sunlight on broken glass and other debris. They also said no shooters were visible on the tape.

Ramsey Clark--a former U.S. attorney general and world-class conspiracy theorist in his own right--believed the Justice Department was lying about Waco. To help him gather evidence in the lawsuit he filed on behalf of the dead, Clark turned to Novel, who claimed to have connections within the CIA and a close friendship with ex-agency director William E. Colby.

Novel pushed the Arkancide theory. He asserted that deputy White House counsel Foster was assassinated in July 1993 "to shut him up" about Waco and that Colby--who drowned in a 1996 canoeing mishap--had been killed because he'd corroborated the FLIR gunfire. (Novel also had an abiding interest in alien technology that he said was hidden at Area 51, but that's another story.)

Seeking corroboration of government misconduct at Waco, Novel turned to Ghigliotti, recognized as one of the best FLIR analysts in the country. Ghigliotti, a Navy veteran who'd also done work for the FBI, wanted no part of it. He considered Novel something of a kook. Besides, the piece of Waco tape Novel brought him, he told me later, was junk--a washed-out, fourth-generation copy, not worthy of analysis.

"I won't put my name on any report unless I can analyze the best available tape," he said. "I don't believe conspiracy bull----." (In Novel's telling, Ghigliotti wanted "too much money" to do the work--$5,000.)

By early 1997, the FLIR gunfire allegations were about to hit the mainstream--as the centerpiece of a documentary film, "Waco: The Rules of Engagement," which premiered at the prestigious Sundance Film Festival and was later nominated for an Oscar. The film's producers got a retired supervisor in the Army's Night Vision Laboratory--a scientist who held several FLIR patents--to go on record supporting the gunfire theory.

Could the FBI be guilty of perjury? Even homicide? I decided to submit the tape to as many experts as I could find. Several were skittish, unwilling to go on the record. They feared government retribution--in the form of IRS audits or being blacklisted from future contracts. One said flat-out that he didn't want to end up dead.

Eventually I got a dozen experts to view the tape. Half of them saw gunfire. The other half saw reflections. I wrote an article in April 1997 concluding that reading FLIR seemed to be more of an art than a science.

Ghigliotti refused to participate then, except as a background consultant. The most scientific way to settle the question, he said, was to re-create the event: Fly a plane over the Texas prairie while men were firing below, using the same FLIR camera as in 1993, then match that tape against the original.

Good idea, I said. But that would probably never happen--unless someone were willing to spend a fortune.

For history's sake, he hoped it would be done. "This needs to be settled once and for all," Ghigliotti liked to say. "We need to have the facts. It's too important not to."

With some coaxing, Ghigliotti finally agreed to offer an analysis if I could supply him the full FLIR record of April 19. He wanted to see and hear the entire context.

Officials at the FBI and Justice Department told me there was only one FLIR video--a silent one that started around 10:42 a.m. (Even though the gassing operation began at 6 a.m.)

Ghigliotti believed the FBI was hiding something. He was right.

Ghigliotti's History

Sometimes, in letters to clients and other writings, Ghigliotti spelled his last name differently: Ghigliotty. When I asked about it, he was evasive. He seemed to enjoy building an air of mystery around himself.

I'd noticed that his resume said he was a minority businessman. What minority? Italian?

"Full-blooded Puerto Rican," he said. "But my family originally came to Puerto Rico from Italy."

Carlos Luis Ghigliotti Jr. was born in New York. He wore a neatly trimmed beard and had light olive features. No trace of an accent. A bit portly--5-foot-7, he weighed 175 pounds--but not fat.

He said his father ran a transmission repair business. He wouldn't discuss his upbringing any further.

Later I learned that his boyhood nickname was Froggie because he enjoyed dissecting frogs in science class. He studied engineering in Puerto Rico, but didn't take a degree. He spent six years working as a machinist's mate aboard guided-missile cruisers.

His father, Carlos Sr., died of heart problems in his sixties. He lost his mother, Sylvia, a heavy smoker, even earlier. She died in Puerto Rico when Carlos Jr., her only son, was in naval training. He flew home immediately.

He told a few close friends the story of how he ended up at her autopsy. Mistaken for a member of the medical staff, he was in the room when the cutting began. The medical examiners found him out and urged him to leave: No man should see his own mother being dissected.

Carlos refused. He was fascinated. He had to know the details.

It turned out she, too, had a bad heart. She was 42 years old.

Analyzing the Man

"I never get sick," Carlos once boasted while I was visiting him with another Post reporter. But that day last September he was nearly crippled by back pain, wincing and barely able to talk at times. Too much stress, we speculated.

He'd been examining tapes for hours on end, late into the night, ever since Waco flared back into the news. "I always see something I didn't see before," he said.

In the rarefied field of IR analysis, Ghigliotti was known for his exceptional equipment and hyper-accurate eyesight--he'd received certification and recognition from the Infraspection Institute for his "outstanding contribution to infrared technology."

But he was just as well known for explosions of temper and willingness to bait his foes in the courtroom, accusing them of fabricating evidence. This hotheaded reputation earned him the nickname "Crazy Carlos."

That day he was scrutinizing FBI tear-gassing tactics and tank movements on some newly obtained videos. For the first time, he was hearing sound on the FLIR tapes--including what he thought was the report of gunfire.

These previously nonexistent FBI tapes suddenly materialized after Attorney General Reno learned that agents had fired potentially incendiary gas rounds at the Branch Davidian complex on the morning of April 19, in direct violation of her orders. The soundtrack confirmed it.

Outraged, she brought in former Missouri senator Danforth, who vowed to answer "the dark questions" about Waco. Among them: "Was there a coverup? Did the government kill people? How did the fire start? Were there shootings?"

Ghigliotti claimed to already know most of the answers. He cued up one of the videotapes I'd given him. It was fuzzy but we could see men with breathing apparatus clustered around the tanks as the compound burned to the ground. According to the FBI, this was a rescue team, hoping against hope to find some Davidians alive.

"Keep your eyes on the section there," Carlos instructed. "There's a whole bunch of firing going on in there, and you see those guys standing up there? They're shooting into the complex."

As reporters, we couldn't say what those flashes were. Ghigliotti, though, was dead certain--and so excited he couldn't stop working. Never mind the pain.

"You can't deny that, okay?" He pointed at a bright smear on the monitor. "I mean, that's undeniable."

The smoking gun? Well, maybe.

Probable Cause

"He didn't know how to let go," the dark-haired woman in sunglasses says solemnly. "He spent many restless nights, insomniac nights with this."

She means Waco: "He was in it. He lived it. He breathed it," Claire Ghigliotti says.

She is stout and speaks with a slight Hispanic accent. Her manner is clipped and no-nonsense. It's easy to see some of Carlos in Claire, his younger sister and sole heir.

She arrives at a restaurant in Crofton driving Carlos's white Crown Victoria--a former police car with dark-tinted windows. He'd rigged it to receive Internet feeds and satellite positioning data; while driving he could also view an infrared camera display, helpful for detecting steam leaks and malfunctioning electrical lines when he did utility work. Carlos loved showing off that car, she says, and even the local cops were impressed.

"He was unique in what he did and how he lived and what he was," says Claire. He could also be described as obsessive.

Carlos was extremely frugal--at least when it came to spending on himself.

He lived in his two-room office, sleeping on an air mattress. Yet he boasted of having spent more than $100,000 on sophisticated gadgetry for his business.

Out of embarrassment, Ghigliotti pretended to have another home. Even friends didn't know of this secret life; I never caught on during my five or six visits to his firm. The building had a bathroom down the hall, and apparently he would check into local hotels to shower, his sister speculates. He was always well groomed.

Claire, a Home Depot receiving administrator who moved here last year from Colorado, says she sometimes wouldn't hear from Carlos for weeks--though they lived just 20 miles apart. She last spoke to her brother April 2 and left him three phone messages thereafter--including an invitation to have arroz con pollo at her place--but figured he was busy or didn't want to see her.

He often traveled to testify in drug and forfeiture cases in which infrared cameras were used. Increasingly, law enforcement relies upon IR to detect the heat of methamphetamine labs and high-intensity "grow lights" used by marijuana cultivators. Ghigliotti would only agree to do defense work for dope suspects in accordance with his personal code: He'd do it just once, and only after they pledged never to break the law again. "He lectured every defendant he worked for," recalls Scott Kremer, a convicted pot grower in California, who says he had to make a donation to a drug-treatment program before Ghigliotti would take on his case.

Nobody knows exactly when Ghigliotti died, but his sister thinks it was April 6. Police found him dressed in nightclothes and lying on the air mattress. They also discovered a grocery receipt--he'd been out shopping on April 4--and some moldy ham and cheese sandwiches. One was half-eaten by his cats.

Simone and Sipowicz--both older, hefty felines--survived. Claire has adopted them.

If not for some of the other tenants' curiosity, Ghigliotti's body might have gone undetected even longer behind the locked, thick metal door to Suite 304. His car hadn't been moved for three weeks. The computer dealers, accountants and secretaries in the building thought that strange; they also may have heard the cats meowing. They notified the management.

Claire figured she would have tracked Carlos down by May 4--to give him a present for his 43rd birthday. Instead she ended up arranging his funeral, calling numbers from a tidy list of 25 names in his wallet.

A Laurel police officer who attended the autopsy let Claire know that her brother most likely died of natural causes. She figured as much: Carlos had a classic Type A personality. He hadn't taken a vacation since 1989. He internalized stress. He didn't smoke, but he didn't exercise. And he didn't eat right: "He was a fast-food junkie," Claire says.

Maryland's chief medical examiner later confirmed that Ghigliotti suffered a heart attack; he had massive arterial blockage. The coroner performed toxicology tests and found no chemical substances except an over-the-counter flu remedy. Nevertheless, on the Internet there continued to be suggestions that Carlos was (a) killed by anthrax, which creates flu-like symptoms, or (b) survives as a government agent--paid off handsomely to allow a pauper's corpse to be planted in his office.

"Let the crazies think what they want to think," says Claire, sounding just as hard-nosed as her brother. She's no believer in conspiracies. Except . . .

"I saw the tapes," she says. Once last fall her brother stayed at her home, paranoid, believing his life was in danger. He made her watch everything.

"He did a second-by-second analysis of where, what, when."

So the FBI is lying?

"Of course," she says. "Every one of them lied."

Claire decided to have her brother buried, not cremated--just in case, she says. Because maybe, someday, he might need to be exhumed.

Contradictory Analyses

One of the last times I heard from Carlos, he was furious. He cursed Dan Burton and said he was through with the congressional committee. "I'm quitting," he said. "The Republicans are more worried about their budget than with finding out what really happened."

Since being retained in October, he had put in five months of work and been paid only $16,100, he said. Now the committee was refusing to fund the hours he felt he needed to complete his work. It also wouldn't pay for a trip to Texas so he could participate in the March 19 Waco gunfire test being staged at the request of Special Counsel Danforth.

That came as a huge blow. Finally, somebody was going to fly over Texas with a FLIR camera--the idea he had years ago--and he wouldn't be in the game.

"He had a delicate ego. He took everything so personally," said David Michael, a San Francisco criminal defense lawyer. "He couldn't separate his personality from his professionalism."

Claire Ghigliotti believes that Congress cut her brother's funds because he got "too close to the truth." But a Government Reform Committee spokesman said Ghigliotti was defunded because the analyst repeatedly failed to produce what the staff considered a "scientific" report.

Ghigliotti wrote a detailed listing of where he detected alleged gunfire, but included no calculations or comparisons based on other IR-recorded muzzle bursts. He said he knew exactly what gunfire looked like, based on his previous experience. He simply ruled out the possibility of sunlight reflections with this statement: "There is no alternative explanation. None."

Burton's investigators didn't think his view would hold up as testimony, unless it were backed with algorithms, models and charts. Ghigliotti maintained that he needed more time for that.

It's hard to imagine that Burton was party to some uber-conspiracy to silence Ghigliotti. This, after all, is a member of Congress who once shot a cantaloupe in his back yard to pursue a theory that a second gunman was involved in Foster's suicide.

Claire has a copy of her brother's preliminary report to Burton, dated March 20. It dissects just one of the FLIR tapes from that day. It counts 70 shots supposedly fired from the weapons of the well-armed Branch Davidians. (The FBI has always said the Koresh forces blasted away at its agents all morning.)

Ghigliotti also counted 57 shots "going into the structure"--gunfire he said clearly came from government positions. He presumed the FBI was simply defending itself, as authorized by the rules of engagement. His eyes also saw seven "unknown subjects" flitting around in the rubble at the back of the collapsed structure near the tanks.

In the months before his death, he eagerly showed several people the "subjects" captured on the FLIR tape, saying these were most likely the FBI gunmen. They were impossible to see until he slowed the film to a frame-by-frame crawl on special monitors, but they were there: spectral gray images that looked and moved exactly like human beings. Or ghosts.

I saw a couple of them myself. Federal forces? Who knows. The government's latest position is that no people are ever visible at the back of the compound where the tanks are.

A new batch of British infrared experts--hired by Danforth's office to simulate the Waco incident and analyze the April 1993 FLIR tapes--says it's all tricks of sunlight. A report from Vector Data Systems found no evidence of a gun battle whatsoever. Just flashes from debris, including a shiny metal plate.

These "thermal events, including the alleged sighting of a person, are all caused by passive specular solar reflection, active thermal reflection or movement of debris," Vector reported.

The FBI was overjoyed when the Vector report came out in early May. "This resolves the FLIR flash issue," an FBI spokesman, John Collingwood, told me. "From our perspective, it lays it to rest."

But the ghosts of Waco never seem to stay at rest. Burton's investigation grinds along. So does Danforth's--last week his staff obtained copies of some of Ghigliotti's files. The civil case in Texas is set for trial June 19.

Houston lawyer Michael Caddell, representing the Davidian side, wanted Ghigliotti to be his expert witness. Visiting the lab in late March, Caddell was astonished at the detail Ghigliotti had coaxed from the FLIR and media tapes with his super-enhancing equipment. He offered him $20,000 for further analysis.

"He had a better handle on this than anyone I've seen," Caddell recalls. "And he was the most reasonable in his assessments."

But Ghigliotti was deeply ambivalent about doing more Waco work. He told his sister it was depressing him. He told me he didn't want to endlessly relive a tragedy that most Americans had long forgotten.

"My current plans (until I met you) were to finish the congressional findings and then take a long vacation," he wrote to Caddell on March 28. "I forgot to tell you that I am currently suffering a rare sickness. It has been diagnosed as Waco fatigue."

What He Left Behind

Carlos didn't have health insurance. When he was feeling ill, he relied on drugstore potions.

At Claire's invitation, I visited his office one last time. The Carlos Bunker--that's what I used to call it. Now, standing amid the accumulated evidence of his short life, that glib journalistic label didn't seem so funny.

I noticed several packets of TheraFlu medication strewn about. He stored Milk of Magnesia and Pepto-Bismol in the small refrigerator. A hoard of painkillers was stashed in desk drawers.

I imagined him rising from a fitful sleep, agitated over FLIR flashes, Dan Burton and the specters of Waco, vainly trying to stave off symptoms of heart disease.

For the first time I noticed a closet, and I found a suit bag hanging there, as well as a small mirror. I saw how he made this place his home. On a shelf sat a mini-stereo and rows of New Wave CDs: He liked the Police, Human League and the Psychedelic Furs. On another shelf was a lone video disc: "The X-Files."

I wondered what had ever happened to the woman, about his age, whom I'd once met working here. She seemed more familiar to him than a temp. I thought maybe they were close. Carlos once mentioned he was looking for a woman to settle down and have children with.

I didn't wonder anymore whether he was right or wrong about Waco. That's for the courts, the prosecutors and Congress to decide. I just wondered how Carlos Ghigliotti, who wanted so much to speak for the dead, forgot how to live.

Mystery Men

Two sailors in blazing white uniforms and white gloves saluted as the hearse pulled up at the Maryland Veterans' Cemetery at Cheltenham. As befit a man who had served his country honorably, Ghigliotti was entitled to a flag-draped casket, a flawlessly performed military ceremony and a decent plot of ground.

The mourners were few--just nine of us, including those who'd met Carlos through his work. We sat close to the front of the sweltering chapel, the better to hear the Catholic priest over the clanking air-cooling system.

The message was entirely clear to me when he cited one of St. Paul's lessons: We live by faith--by believing, not by seeing.

There was a stir in the back of the room as a knot of dark-suited men arrived. They sat off to the side, by themselves, five of them. They exited hastily after the ceremony, not pausing to greet Claire or anyone else.

They departed in an SUV behind smoked windows. None of the mourners had any idea who they were.