WHEN ROBERT F. Kennedy was mortally wounded on June 5, 1968, the gunman fired his weapon out of a crowd of at least 77 people. The New York senator, who had just won the crucial California primary, was surrounded by his entourage, reporters, hotel personnel. All were crammed inside the narrow kitchen pantry of the Ambassador Hotel in Los Angeles when the shooting started.

It seemed natural, then, to accept the official version: that Sirhan Bishara Sirhan, a young Palestinian immigrant, was the one and only shooter. The idea of Sirhan as a classic "lone nut" quickly became the common wisdom in the minds of most Americans.

Even so, almost 22 years later, serious questions remain. There are contradictions in eyewitness accounts and questions about the physical evidence. Some of this evidence points to the strong possibility that a second gun was fired.

In spite of the doubts, though, no one has made a systematic attempt to accumulate evidence from the most objective and experienced witnesses available -- the police investigators themselves.

This article does that. Using the LAPD's active roster and pension records, I located and interviewed more than 100 of the LAPD officers and sheriff's deputies who were involved in the investigation in the hours and days after Robert Kennedy was shot. My aim is not to deny Sirhan's role in the shooting, or to establish a particular conspiracy theory. But evidence at a crime scene often has a logic of its own.

Over the years, there have been periodic attempts to reopen the case. A court-appointed panel in 1975 reviewed police testimony that only Sirhan's gun could have fired the intact bullet reportedly removed from Kennedy's body. It could not sustain that con-clusion -- a finding that undermined an important evidentiary pillar in the trial of Sirhan.

Another challenge has come from the testimony of a dozen or so people in a position to witness Sirhan fire his weapon. Their version of events casts serious doubt on the police reconstruction -- which is that Kennedy was killed by point-blank shots. There are also apparent inconsistencies between the presumed paths of some bullets and the wounds they caused.

Most troubling, though, is evidence that more bullets were fired than could be loaded into Sirhan's eight-shot, Cadet model Iver-Johnson .22 revolver. It is on that discrepancy that my investigation focused: If nine or more bullets were discharged, then a second gun must have been fired in the room when RFK was shot.

I believe that the evidence of at least nine bullets is substantial.

The murder investigation originally was conducted by the Los Angeles Police Department and, to a lesser extent, the FBI. Official police reports agreed that eight bullets caused all the damage, and according to these reports, Kennedy was shot three times at point-blank range; five other victims, all of whom survived, were each shot once. Seven of the eight bullets reportedly fired from Sirhan's gun were recovered, according to the LAPD, and one was lost in the ceiling space of the pantry.

But there was evidence of other bullet damage in the kitchen pantry of the Ambassador. In fact, the LAPD's own uncaptioned photographs show that the wooden center divider on the door frame, where bullets holes had been reported by eyewitnesses, had been removed and replaced. Chicago Tribune reporter Robert Wiedrich, who was permitted on the scene within hours after the shooting, wrote the next day that he had seen "on a low table an 8-foot strip of molding, torn by police from the center post of the double doors leading from the ballroom . . . . Now the molding bore the scars of a crime laboratory technician's probe as it had removed two .22 caliber bullets that had gone wild." (Wiedrich, who is still at the newspaper, told me last week that he hadn't previously realized the significance of what he had written.)

FBI photographs and accompanying captions, which identify bullet holes in door frames, were later said by LAPD officials to picture no more than ordinary wear and tear; there is no specific reference in the LAPD's final report, property reports or analyzed evidence reports to suspected bullet holes in the walls and door frames in Sirhan's line of fire.

When police officials are asked about eyewitness accounts, they refer -- quite understandably -- to the panic and confusion that broke loose inside the pantry while Sirhan was shooting into the crowd. As for bullet damage, officials have said the sightings were made by people who are not trained in such observations.

A 1987 article I wrote for Regardie's magazine challenged the LAPD's crime-scene investigation by quoting such civilian eyewitnesses as Angelo DiPierro, the hotel's maitre d', who signed an affidavit in 1975, saying that following the shooting he had noticed "a small caliber bullet lodged about a quarter of an inch into the wood on the center divider of the two swinging doors . . . . I am quite familiar with guns and bullets having been in the infantry for 3 1/2 years."

The story was credited with contributing to the decision by the City of Los Angeles to release its investigative files in the Kennedy case. The records of the police investigation were sent to the California State Archives in Sacramento and released to the public in April 1988. Such a release of these vital police records had been promised, and postponed, for years.

These documents showed that police spokesmen had often been inaccurate in their representations of key facts in the case. They also confirmed that important material evidence had been destroyed.

Last December, I began to approach professional law enforcement personnel who had worked on the investigation, knowing that their training and experience, unlike that of the civilian witnesses, could not easily be challenged.

Only a handful, I learned, had been questioned about the case by anyone outside the LAPD. None of those interviewed seemed to recognize the significance of their statements when they identified one or more bullets or bullet holes in a wall or door frame in the kitchen pantry.

I did not inform the officers of the significance of additional bullets at the crime scene because I did not want to influence their objective recollections. In the course of our interviews, I asked two basic questions: "What did you do?" and "What did you see?" Some could no longer remember details, but others had clear recollections concerning the investigation.

Most did not have access to the roped off, well-guarded kitchen area. However, the responses of those who did were often revealing. Among the respondents (most of whom are now retired) were these:

LAPD photographer Charles Collier, who had been with the department since 1952. When I pressed Collier as to how sure he was that what he took pictures of were bullet holes, he replied, "A bullet hole looks like a bullet hole -- if you've photographed enough of them." Only 51 of the 98 official numbered photographs Collier apparently took at the crime scene have been accounted for.

Patrolman Al Lamoreaux, who told me, "I do recall seeing one or two holes in the door around wherever he had shot at him . . . . It was just obvious. Just being a dumb cop, you look and see where the bullets went."

Sgt. James R. MacArthur, the senior LAPD detective at the crime scene, who said that he had seen "quite a few" bullet holes and specifically remembered one that hit high on the wall to the immediate left of the swinging doors at the west end of the pantry -- in Sirhan's line of fire.

Lt. Albin S. Hegge, who coordinated and catalogued information coming in from the hotel. He also remembered that bullets were recovered from the scene. He said, "I know there were some, because they took out {door} panels. I mean, they cut them out and saved them . . . . And they took them down to the lab so that they could examine the bullets."

Officer Kenneth E. Vogl, who was assigned to guard the crime scene during the crime lab's investigation. He told me that he discovered two .22 fragments on the floor. When I asked Vogl to tell me on a scale of one-to-10 -- with 10 being absolute certainty -- whether what he had seen were bullet fragments, he replied, "Oh, it was a 10. There's no doubt. I saw fragments." Vogl added that he had reported these discoveries to one of the LAPD officials at the scene. However, no bullet fragments were ever booked or even reported at the crime scene.

Officer David Butler, an LAPD Medal of Valor winner. He was part of the Scientific Investigation Division team at the crime scene, though he was not listed in official police records as being among those there. When I asked Butler during our first interview who had recovered bullets that night, he replied, "{SID officer} DeWayne Wolfer took the two bullets out of the wall," adding that he had been present when the bullets were removed.

A month later, in a second interview, Butler had a different recollection: that he'd only seen what he believed were bullets that had been "photographed, labeled, then packaged, catalogued" in small evidence packages. These packages, he recalled, were marked either "bullet evidence" or "firearms evidence." Regardless of which version is correct, there is no official report of any such evidence being recovered or booked from the crime scene.

Sgt. Raymond M. Rolon, a top official at the crime scene, who told me that during a tour of the pantry, "One of the investigators pointed to a hole in the door frame and said, 'We just pulled a bullet out of here.' "

In addition to these LAPD officers, other official personnel who saw bullet damage in the hotel kitchen include:

Los Angeles Sheriff's Office Deputy Thomas Beringer, who had been among the first law enforcement officials at the hotel to help clear the crime scene after the shooting. Beringer said, "I remember one person {dressed in a tuxedo} trying to take a bullet out of the {door frame} with a knife, a silver knife, for a souvenir."

LASO Deputy Walter Tew, who had actually circled four bullet holes in two door frames and scribbled his name, "W. Tew," his badge number, "723," and "LASO" inside each circle. {See photo on this page.} Tew died in June 1988. Sgt. John C. Barber, another member of the LASO contingent at the crime scene, explained that Tew had, in fact, identified bullet holes. "That would be the typical way a deputy sheriff in that era would mark his evidence." No mention of Tew appears in the LAPD records in Sacramento.

Los Angeles County Coroner Thomas Noguchi, who performed the autopsy on Kennedy. Noguchi also participated in the LAPD's crime scene reconstruction. In a 1975 affidavit, Noguchi said that during the reconstruction, "I asked Mr. Wolfer where he had found bullet holes at the scene . . . . He pointed to several holes in the door frames of the swinging doors leading into the pantry . . . . I got the distinct impression from {Wolfer} that he suspected that the holes may have been caused by bullets."

FBI Special Agent William A. Bailey, who also signed an affidavit in 1976, which stated, "At one point . . . . I (and several other agents) noted at least two (2) small-caliber bullet holes in the center post of the two doors leading from the preparation room {the pantry}. There was no question in any of our minds as to the fact that they were bullet holes."

Bailey told me, "I am absolutely certain that I saw bullet holes. And when I inspected those bullet holes, I clearly saw the bases of two .22 caliber bullets in those holes."

FBI Special Agent Alfred C. Greiner, who conducted a survey of the crime scene two days after the shooting. He filed a report, accompanied by captioned photographs, taken by FBI photographer Richard Fernandez, identifying four "bullet holes" in the door frames of the pantry. Greiner declined to be interviewed for this story. Fernandez, still employed by the FBI, did not have permission to speak about the case, according to Fred Reagan, an FBI spokesman in Los Angeles. The FBI has refused to respond to any direct questions about its own official report.

Roger LaJeunesse, the principal FBI special agent assigned to the case, said last week that he hadn't previously recognized the significance of the FBI photographs. "I didn't pay any particular attention to them, because I knew that the pictures Fernandez took and Greiner supervised were for the purpose of witness orientation," he said in an interview. "The SID had the responsibility for preserving crime-scene evidence. If these are, in fact, bullet holes, their origin should have been determined."

LAPD spokesmen say that the department stands by its initial conclusions. Robert A. Houghton, the LAPD's former chief of detectives who supervised the Kennedy murder case, took a similar view last week. But he added, "If concrete evidence exists that Sirhan did not kill Senator Kennedy or that there was a conspiracy involved, then the case should be reopened." Houghton, when asked about sightings of bullet holes, referred a questioner to the official record.

DeWayne Wolfer, who testified under oath in a 1971 civil proceeding that no bullets were recovered at the crime scene, also refused to be interviewed. So did Sergeant William J. Lee, who was Wolfer's second-in-command. Both men are now retired. Wolfer has been under fire for years because of his handling of the evidence in this case.

Nearly 22 years later, it will not be easy to re-open the investigation. Officially, the department says that the case is closed. Door frames and ceiling tiles booked as evidence from the crime scene have long since been destroyed by the LAPD.

Still, based upon the statements of those I interviewed, there are strong reasons to believe that more than eight bullets were fired that night. In fact, current available evidence suggests that 12 or more bullets may have been fired, which is consistent with the initial FBI report on this matter.

At the conclusion of my interview with Sgt. MacArthur, I showed him the official LAPD document, accounting for all eight bullets fired by Sirhan. I then explained the significance of the additional bullet holes. Shocked, MacArthur said that if the facts as I presented them are correct, the case should be reopened. (A spokesman for Sen. Edward Kennedy's office said he stands on previous statements that the evidence should prevail, adding that there would be no further comment.)

We live in a nation whose history over the past three decades has been tragically altered by political assassination. We owe it to ourselves to learn as much of the truth about this case as it is possible to know.

Dan Moldea, a Washington writer, is the author of "The Hoffa Wars," among other books.