By Jerry Markon
Washington Post Staff Writer
Tuesday, September 21, 2010; 11:43 PM
The anonymous call came in the middle of the night, from a phone booth near Madison, Wis. "Hey, pig!'' a male voice warned. "There's a bomb in the math research building.''
It was 1970, the height of student demonstrations against the Vietnam War. The pig, in the vernacular of the times, was a police dispatcher. And the bomb was real, a novel device that exploded minutes later on the University of Wisconsin campus, causing massive damage and killing a researcher who was the father of three young children.
The devastation triggered an intensive FBI manhunt for one of the bombers, a frustrating quest that 40 years later has become the ultimate cold case. The quarry is Leo Burt, who has eluded the FBI longer than any other fugitive who made its Ten Most Wanted List. A prominent figure in the annals of domestic terrorism, he is virtually unknown to the general public.
Now the search is heating up again. New tips have flowed to the FBI in recent months, and the bureau is taking advantage of the bombing's 40th anniversary to bring new attention to the case in the hopes that the publicity might lead them to Burt.
Burt, 62, is the final suspect in what is known as the Sterling Hall bombing. The August 1970 explosion, which targeted an Army-funded research center, stood for a quarter-century as the largest act of domestic terrorism in U.S. history until the Oklahoma City bombing in 1995.
It was the first time bombers had packed major explosives in a vehicle, and authorities say it ushered in the modern era of terrorist truck bombs. It also marked a turning point for some in the antiwar movement, who were disturbed by the violence.
A former altar boy and ROTC student who embraced left-wing politics, Burt is thought to be the last of the Vietnam-era radicals pursued by the FBI. His trail has tantalized for years, with false sightings at a Denver homeless shelter and a Costa Rican resort among hundreds of tips.
Some say he's dead - or was a government plant. Authorities at one point suspected he might be the Unabomber. He has been compared to D.B. Cooper, the hijacker who parachuted out of a jetliner with $200,000 and vanished.
"We have a state bird and a state flower,'' said Michael Zaleski, who prosecuted one of Burt's three alleged co-conspirators, all of whom were caught in the 1970s. "Leo Burt is the Wisconsin state ghost.''
Longtime FBI director J. Edgar Hoover - determined to crack down on student activist groups - took charge of the investigation in the final two years of his life. In recent years, especially in the past few months, agents have intensified their efforts with periodic help from the FBI-led Joint Terrorism Task Force and legal attaches overseas. For the 40th anniversary of the bombing, the FBI highlighted the case online and recirculated Burt's "wanted" poster.
"He needs to be held accountable for what he did,'' said FBI Supervisory Special Agent Chris Cole, who oversees the Madison office.
Yet even as agents are tracking dozens of new tips, Burt's fate remains a mystery. "It's not like we've gotten a call from someone saying, 'I was Leo Burt's ex-girlfriend, and I know where he is,' '' said one federal law enforcement official, who spoke on the condition of anonymity to discuss the investigation in detail. "That makes someone hard to find.''
Leo Frederick Burt grew up in a close-knit Catholic family in the Philadelphia suburbs. Athletic and muscular, he attended parochial schools and dreamed of being on the Olympic rowing team.
"He was a red-blooded all-American type, salute the flag, hard-working,'' said Randy Jablonic, the rowing coach at the University of Wisconsin when Burt arrived in the mid-1960s.
He joined the rowing team and spent a summer at the Marine Corps officer candidate school at Quantico.
"What set him apart was his haircut,'' said Jack Holzhueter, Burt's journalism instructor. "In this era where everyone is growing their hair out, he practically had a shaved head.''
An aspiring journalist, Burt had been a sportswriter for the Daily Cardinal, the student newspaper, which was closely linked to the antiwar demonstrations at the campus.
Burt let his hair grow. He began covering the protests and was beaten by police during a riot, said Joe Brennan Jr., who researched the case as a graduate student at Johns Hopkins University.
Burt later told Holzhueter that his time at the Cardinal radicalized him.
By 1970, authorities said, Burt had joined a local antiwar group known as the New Year's Gang. It acquired that sobriquet from a keystone-cops adventure in which members stole a small airplane on Dec. 31, 1969, and flew it over an ammunition depot. They tried to drop molotov cocktails, but none exploded.
The next target was Sterling Hall, a campus building that housed the Army Math Research Center. It performed defense-related work, incensing student demonstrators.
Burt and fellow gang member Karleton Armstrong took the lead, according to Zaleski and former FBI agents. The pair interviewed farmers and read materials on "stump blowing,'' a technique farmers used to remove stumps from their fields.
They constructed a sophisticated device mixing ammonium nitrate and fuel oil, eerily similar to the bomb that destroyed the Oklahoma City federal building.
On Aug. 24, a warning call went out at about 3:40 a.m. to Madison police telling them to clear the building. A stolen Ford Econoline van, containing six 55-gallon drums, was parked outside.
Two minutes later, the bomb went off. People within 30 miles heard the explosion. Pieces of the truck were found on eight-story buildings blocks away. More than 30 buildings were damaged; parts of Sterling Hall were destroyed. Ironically, the Army lab was barely damaged.
Inside Sterling Hall, Robert Fassnacht, a 33-year-old physics researcher studying superconductivity, had been working late.
He was planning to take his wife, 3-year-old son and 11-month-old twin daughters on vacation to California that day, said his sister, Carol Humphrey.
It was his son's birthday.
Graduate student David Schuster recalls seeing Fassnacht in a basement hall, coat and backpack on, apparently ready to leave.
Schuster walked into his office and was knocked unconscious by the blast. He awoke buried in rubble, his ears ringing and shoulder broken.
"By all rights, I should be dead,'' said Schuster, now a physics and science education professor at Western Michigan University.
Schuster was one of four people injured. Fassnacht was killed.
In Washington, the Nixon administration reacted with alarm. "The powers-that-be wanted to squelch this,'' retired FBI agent Allan James Thompson said. "You had radicals marching around the country, and now doing this. They wanted to make an example of these guys.''
Thompson and about 60 other FBI agents descended on Madison. They tracked the white Chevrolet Corvair seen speeding from the bombing and traced the van's vehicle identification number.
Hoover "was apprised of everything. He made all the decisions,'' Thompson said.
On Sept. 2, Hoover announced a nationwide manhunt for four men: Burt, 22; Armstrong, 22; his brother, Dwight Alan Armstrong, 19, and David Fine, 18. They were put on the FBI's most wanted list.
The men were charged with conspiracy, sabotage and destruction of government property, and the FBI said Karleton Armstrong "reportedly is a strict vegetarian, speaks Spanish and allegedly is a drug user.''
The Washington Post reported, without attribution, that Burt was "said to be an admirer" of Cuban leader Fidel Castro.
The New Year's gang took responsibility for the bombing in a letter cited in an FBI affidavit.
"While we mourn an unnecessary death,'' the letter said, "we celebrate the blow to U.S. imperialism.''
Burt was traced to New York, Boston and then Canada, where many antiwar demonstrators fled to escape the draft.
Days after the bombing, authorities said Burt escaped with Fine out the back of a boarding house in Peterborough, Canada. Royal Canadian Mounted Police were converging in front.
Burt left behind a wallet with a fake ID: Eugene Donald Fieldston. The name is still cited on his FBI wanted poster.
Then he vanished.
At first, agents worked the case 24-7. Over the next seven years, three of the men were caught. They pleaded guilty, served prison terms ranging from three to eight years and resumed their lives.
Karleton Armstrong now runs a juice stand near Sterling Hall. His brother, Dwight, died of cancer this year. Fine is a paralegal in Oregon.
Agents say that Burt's trail was cold from the start and that by 1976, it had gone frigid. He was taken off the most wanted list that year.
The FBI maintained at least one agent on the case. At one point, agents sent Burt's fingerprints - obtained during his summer at Quantico - to all coroners and medical examiners in America to compare with John Does.
They monitored the funerals of Burt's parents, knowing that fugitives often trip up by contacting family members. Nothing.
In the 1990s, a new theory emerged: that Burt was the Unabomber, who had begun mailing explosive devices in the late 1970s.
Some agents saw a resemblance between Burt and the famous artist's sketch of the Unabomber wearing a hooded sweat shirt and dark glasses. Others detected similarities in Burt's college writings and the Unabomber's famous "manifesto.''
"They were just the sort of things to make you say, 'Well, I wonder if this is the same guy,'' said retired FBI agent Kent Miller, who led the search from 1995 to 2003.
That thread ended when Theodore Kaczynski was arrested in 1996 in the Unabomber case. But the search for Burt moved into a new phase with the growing use of the Internet.
Tips started flowing. Someone in a Denver homeless shelter thought "a spooky guy who never stayed more than three nights" was Burt, Miller said. Agents retrieved the man's fingerprints.
Other reported sitings, all false, came from as far as Algeria.
The FBI persuaded the television show "America's Most Wanted" to feature the Burt case and the agency is publicizing a $150,000 reward.
Humphrey, Fassnacht's sister, suggests that the government should go easy. "If he's been a good law-abiding citizen, it might be a disservice to prosecute him,'' she said in an interview, adding that she has "reached the point of forgiveness.''
Cole said the bureau's working assumption is that Burt is alive and has a new identity.
"We will not stop,'' Cole said, "until we catch him or have credible evidence that he's dead.''
Staff researcher Julie Tate contributed to this report.