updated 8:27 p.m. ET July 17, 2009

NASHVILLE, Tenn. - Ex-NFL quarterback Steve McNair's mistress bought the gun she used to kill him from a convicted murderer whose fiancee was afraid to have it in the house, authorities said Friday.

Adrian J. Gilliam Jr., 33, of La Vergne, Tenn., was charged with being a convicted felon in possession of a firearm. He admitted selling a 9 mm Bryco/Jennings to Sahel Kazemi for $100, according to court documents.

Kazemi, 20, shot McNair to death at his condo July 4 before killing herself. Authorities say she met Gilliam while she was trying to sell her car and told him she was looking to buy a gun.

A criminal complaint says Gilliam - who was convicted in 1993 in Florida for murder and attempted armed robbery - told police he sold the gun to Kazemi, whom he identified from a police photo.

Detectives traced the gun to its 2002 sale at a pawn shop. Gilliam eventually bought it from someone for $100 about a year or year and a half ago. Investigators said he told them he bought it for protection after his home was burglarized, and police reports show a burglary around that time.

Nashville Police Chief Ronal Serpas said at a news conference Friday that Gilliam decided to sell the gun because his wife was afraid to have it in their house.

Federal Public Defender Hugh Mundy said Gilliam is not married but is engaged to a woman with whom he has a 2-year-old daughter.

Slideshow   A Titan dies See the career highs and lows of former NFL quarterback and Tennessee Titans legend Steve McNair, who was found dead on July 4. more photos

Gilliam has been out of jail for seven years and has had no other trouble with the law in that time, Mundy said.

"No one denies this is a tragedy," he said. "Steve McNair was one of Nashville's heroes. A lot of lives have already been ruined. But Mr. Gilliam is a decent, hardworking family man and there's no reason to ruin his life too."

Gilliam's father, Adrian Gilliam Sr. of San Antonio, Texas, told The Associated Press Friday night his son had been "keeping straight" since his release from prison.

His son has been working as a car salesman "and taking care of his family," his father said.

"He's pretty good at it. He's a pretty sharp young man."

Police had said last week that Kazemi purchased "a fully loaded 9 mm pistol from a private individual" who met her in the parking lot of the mall where she worked at the Dave & Busters restaurant. That's also where she first met McNair. The sale took place two days before the shooting.

Authorities believe McNair was likely asleep when Kazemi put the pistol to his head and pulled the trigger. She put two more slugs into his chest and a fourth bullet into the other side of his head before shooting herself.

McNair, a married father of four, walked away from the NFL last year. "Air McNair" was known as a gutsy quarterback who played through serious injuries and led his Tennessee Titans to a Super Bowl.

U.S. Attorney Edward Yarbrough said Kazemi's age did not make the sale of the gun illegal. A licensed dealer is barred from selling a gun to someone younger than 21, but private sales to people older than 18 are legal, he said.

Convicted felons, however, cannot have guns. Jim Cavanaugh, the Bureau of Alcohol, Tobacco, Firearms and Explosives special agent in charge in Nashville, held up a pistol similar to the one used to kill McNair and said, "A convicted felon cannot receive it, possess it, buy it, store it, hold it, shoot it, aim it, clean it, or do anything with it."

Gilliam faces up to 10 years in prison and a $250,000 fine. He was in court Friday afternoon, but a hearing to set bond was delayed until Wednesday.

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