Alan H. Rotton, a 42-year old FBI supervisor who said he felt his life was ruined after being fired Tuesday for alleged corruption, apparently killed himself yesterday.

In a two-hour interview 24 hours before his death, Rotton talked coolly, calmly and grimly about the dismissal. "It's humiliating," he said. "My career is ruined. I don't know what I'm going to do." He gave no sign then, though, that he was so despondent that he would take his life.

Rotton was found shortly after noon in the garage at the home of his wife in suburban Burke. Sources said he left a farewell note to his family -- he had three school-age daughters -- and had called his headquarters' superior to thank friends who had stood beside him during the bureau's internal investigation.

He reportedly told his supervisor, John Lawn, of the background investigations section, that he wanted him to take care of the insurance money for his wife. Lawn immediately alerted Fairfax County police and left for the home. But authorities arrived minutes too late.

A Fairfax County police spokesman said the death was listed as an "apparent suicide," pending an autopsy. Rotton was still alive when authorities arrived at the scene, but soon died of a bullet wound to the head, the spokesman said. A snub-nosed revolver was found nearby, but was not his FBI firearm. That and his badge had been taken from him Tuesday.

Rotton agreed to talk with a reporter Thursday with the understanding that nothing from the interview would be used until his case was before the courts. We met at the Twin Bridges Marriott shortly after noon and, because the coffee shop was filled, we drove to the end of the parking lot in his red-and-white Ford pickup truck and talked.

The 14-year bureau veteran talked dispassionately about the predicament he was in, saying he expected to be indicted and convicted because the wiretap evidence looked overwhelming. He claimed, though, that he never stole any money intended for informers or profited from a theft ring, as was alleged.

He said he had no lawyer yet because he had no money. "I had $200-a-month house payments in Kansas City." he said. "The move to Washington was a disaster."

Rotton seemed relaxed as he described his life as a field agent in Kansas City from early 1967 to January 1978. He occasionally lit a cigarette or played with aviator sunglasses while recalling the difficulties of cultivating the criminal informers whose testimony led to his dismissal.

Rotton said he first learned of the internal investigation last summer when Robert Joseph Martin, a longtime informer friend, called to say that other agents were going around asking questions about payments Rotton and another agent had reported making to informers.

An affidavit filed late Tuesday in Kansas City to support a search warrant in the case alleged that other informers said they did not receive thousands of dollars that FBI receipts said the two agents collected on their behalf.

Rotton said he learned later that officials of the Missouri, Kansas and Texas Railroad, who were under investigation, told federal prosecutors last May that "before you get us in the grand jury, you'd better clean your own house."

The railroad executives accused him, he said, of stealing cigaretts from a boxcar, accepting gratuities such as a rolltop desk, and failing to report the continued looting of a rail switching yard in Eve, Mo.

Rotton said he gave the cigaretts to an informer to boost the latter's credibility with suspicious gang members.

An FBI check with the informer led to the allegation of the missing informer fees.

"It's interesting," Rotton said. "I know they can't trace that money to me. So it's the word of the informants against me and [agent Stephen S.] Travis. We're in the kind of box that lots of agents could get in."

Rotton acknowledged, though, that the wiretapped conversations seemed to supply overwhelming evidence that he was trying to influence a witness in the investigation.

At one point he is quoted as suggesting to Travis, who was implicated and forced the resign in the case, that he might have to "orchestrate the [informer's] testimony a little bit."

Equally damaging, Rotton admitted, where the references where he and Travis laughed about Martin's success at occupying a rail detective while MARTIN'S GANG BROKE INTO BOXCARS. he's sitting on the railroad dick while the rest of them cary off the railroad," Rotton was quoted as saying.

At another point, the affidavit said Rotton asked Martin to keep him in mind "if you hit that place again and find a freezer."

During the interview Thursday, Rotton said he "might have made remarks like that, but they were said in a light-hearted way . . . I'm afraid a jury will find them convincing, though."

Rotton seemed most distressed by what he viewed as the FBI's hypocrisy about its dealings with criminal informers.

The bureau has strict guidelines about the use of informers, which include a general ban on allowing them to participate in crimes. "The policy is one thing, the practice is another," Rotton said the night he was fired. "Any informant the bureau's got is involved in illegal activities. How else are you going to get the information?"

He elaborated on his thoughts about informers Thursday. He said in the Hoover era it was likely that half the informers listed in bureau files never existed, or never provided any information.

Rotton seemed worried about Martin because his name had surfaced in the affidavit, and Rotton said he believed the informer's life as in danger.

"Handling criminal informants is a real pain in the a --," he said. You have to worry about them all the time, get them out of trouble . . . You just hope you get more [information] than you give up [through informers' crimes]."

Rotton said he had become friends with Martin because he had been dealing with him for 10 years. He placed a call to the informer shortly before his death yesterday.

Martin declined to discuss the call or Rotton's death in a short telephone conversation from Kansas City. "I'd rather not comment," he said. "The more my name comes up in the paper the more trouble I'm in. I don't know what to say."

Officials who took part in the investigation of Rotton and Travis said they were amazed at how blase Rotton seemed when informed in August that he was under investigation. His attitude changed Tuesday, when FBI internal investigators confronted him with a stack of the wiretap transcripts, sources said. But he refused to resign and was fired instead.

"You can imagine how humiliating all this is," Rotton said Thursday. "I was close to Director [Clarence M.] Kelley. I drove him when he came through Kansas City."

He added, "Of course, he didn't know anything about any of this. I just hope he's not embarrassed by it."

Rotton said he stayed in Kansas City for 11 years because he didn't want to take part in the normal advancement programs that would tie him to a desk. He came to Washington in early 1978 on a routine transfer, and worked as a desk supervisor, reviewing background checks on government job applicants.

He had been living in a $400-a-month apartment in Crystal Towers in Arlington since February. He didn't talk about his family in the interview Thursday.

The case against Rotton and Travis was the first involving alleged corruption by FBI agents Joseph Statbile was indicted last year on charges of lying about a $10,000 bribe from an organized-crime figure. Stabile pleaded guilty and was sentenced to prison.

FBI and Justice Department officials issued statements of condolence to Rotton's family yesterday.

FBI Director William H. Webster said, "I regret this sad occurence and offer my sincre condolences to Mr. Rotton's family."

Michael E. Shaheen Jr., who coordinated the investigation of Rotton and Travis from the Justice Dpartment's office of professional responsibilty, echoed Webster by saying, "We deeply regret Mr. Rotton's death and the anguish it will cause his family and friends."

Shaheen had praised the FBI Tuesday for its aggressive investigation in the case.

Rotton said in the Thursday interview that he was surprised to learn that bureau official had approved wiretaps on colleagues.

At the end of the interview he seemed resigned to the fact that he would go to jail, but agreed to talk again when his expected indictment was returned. g"There's more to all this that the public ought to know to put it all in perspective," he said "Let's keep in touch."