When George Peter Valltos decided to celebrate a friend's 40th birthday at a Gaithersburg hotel lounge Saturday night, his wife Yvonne said she stayed home because she couldn't get a baby sitter and she doesn't like bars "because weird things happen."

Exactly what happened Saturday night at the Sheraton Potomac is still unclear. But about 20 minutes after he arrived at the hotel's Ricky's Lounge, Valltos got into a tussle in the parking lot with a moonlighting Montgomery County police officer. Valltos allegedly grabbed the officer's foot-long flashlight, according to police, who said the officer drew his revolver and fired twice.

Valltos, who had a history of drug and mental problems, according to court records, died hours later from two bullet wounds in his shoulder and stomach.

"Why did it all have to happen? Why did he have to shoot him?" Yvonne Valltos, a mother of five, said through tears yesterday. "It seems so out of proportion to what was going on . . . . The whole thing seems crazy. He was in a nice suit at a nice place . . . why did this happen?"

Montgomery County police yesterday had few details to add to the investigation of the death of Valltos, 37, of 19515 Frederick Rd., Germantown, who was shot by Officer Harold K. Allen, a three-year member of the county police force. Allen was working in civilian clothes as a part-time security guard at the hotel Saturday night. The officer was uninjured in the fight, police said, and has been placed on administrative leave with pay until an investigation is complete.

"The use of deadly force is obviously part of the investigation," said Sgt. Harry Geehreng of the Montgomery County Police Department. Geehreng would not elaborate on specifics of the Valltos case but said that department policy allows an officer to shoot in defense "for what he perceives to be an immediate threat of death or serious bodily injury."

Warning shots are not allowed. If an officer opts to shoot, he is shooting to kill, Geehreng said.

Police said Saturday's shooting occurred shortly after 10 p.m. when Valltos was asked by a hotel manager to leave the bar because he was "boisterous."

In a few minutes, Valltos attempted to return to the bar and Allen, called by hotel security, then escorted him to the parking lot. The two men scuffled in the parking lot and Allen's flashlight fell to the ground. Valltos picked it up in an attempt to attack Allen, police said, and Allen fired his .38-caliber revolver twice, police said. Police said Allen had identified himself as a police officer.

Police would not say whether anyone else saw the parking lot confrontation.

Valltos died after surgery about 4 a.m. Sunday at Suburban Hospital.

Friends and family recounted what they knew about the fight in shocked tones yesterday. Valltos was one of a group of friends celebrating the 40th birthday of Shirley Burdette, a bus aide for Montgomery County schools. They were meeting at the Sheraton because they wanted to drink and dance. They didn't expect to be out late because, as Burdette said yesterday, "I wanted to go to church the next morning."

"We were dancing and having a good time and George decided to do a Greek dance by himself out there. He was dancing with his arms stretched out and kicking his legs. It was just George trying to be funny . . . then I saw the manager walk over and talk to him," Burdette said. "I didn't know what was going on . . . next thing I knew another friend came over and said 'George has been shot.' "

George Valltos was no stranger to trouble. Since he served with the 101st Airborne Division in Vietnam and returned to the United States in 1970, he had a history of mental problems and drug addiction, according to Montgomery County Court documents.

In 1976 he was convicted of a break-in at a Silver Spring variety store and sentenced to two years in state prison. In 1980, he was found guilty of robbery, assault and battery and assault with intent to maim for an attack in which he stole a knife. He was sentenced to five years in prison, which was suspended, and placed on supervised probation, according to court files.

An August 1976 court document, filed by his attorney, said that Valltos had a "long history of mental illness that originated in 1970 when he had a breakdown while serving in the armed forces in Vietnam. He has been an outpatient at the Veterans Administration Hospital in Washington since 1970 . . . . In the past he has suffered from auditory hallucination, suffered personality disorders and been addicted to drugs," the court file said.

A March 1984 notation in his court file said that Valltos' "psychiatric problems are chronic and treatment at the Veterans Administration was indefinite."

Yvonne Valltos acknowledged that her husband, who worked intermittently as a cook and a painter, had suffered stress from his Vietnam experience. What she couldn't understand was how he could survive a war and die in a parking lot.

"He wasn't robbing a bank. He wasn't sexually molesting a child. He wasn't doing anything to deserve murder but that's what he got," she said. "Why in the world would you shoot somebody for picking up a flashlight?"