William Lenox, 31, hadn't paid rent in a few months and was in a rage when he kicked in the door to his Bay Point residence Feb. 19 and threatened his roommate, prosecutor Harold Jewett said Tuesday.

The argument ended when Lenox's roommate Andrew Mahler, 33, fatally shot Lenox in the abdomen inside their residence at 44 Pensacola St. in the unincorporated community of Bay Point.

Mahler was arrested for murder, but Jewett, supervising attorney with the Contra Costa County District Attorney's office, declined to file charges Friday saying that Mahler shot Lenox in self-defense.

Mahler was released from county jail Friday, Contra Costa County Sheriff's spokesman Jimmy Lee said.

On the day of the killing, Mahler, who had apparently locked out Lenox, had been in the kitchen eating spaghetti when Lenox, a 6-foot 3-inch-tall, 250-pound man with a history of violence and methamphetamine use, broke through the door and started punching holes in the walls.

The dispute over Lenox's failure to pay rent had been ongoing and a couple weeks earlier, Lenox had "kicked Mahler's ass," a witness told investigators, Jewett said, a fact that made Mahler believe Lenox planned to follow through on his current threats.

Mahler, who was also a large man, retreated to his bedroom, Jewett said, but Lenox kept coming at him. He punched a hole through Mahler's bedroom door and continued to threaten him.

Mahler grabbed a gun, which he owned legally, and fired a warning shot into the floor, Jewett said, but Lenox kept coming at him.

"At this point the gun is up for grabs," Jewett said.

If Mahler didn't shoot Lenox, he was in danger of having Lenox grab the gun and use it on him, Jewett said.

"Mr. Mahler did have a right to arm himself," Jewett said. "Mr. Lenox had a duty to retreat. He charged at a man with a gun who had a right to have a gun and at that point shooting him was the only option left," Jewett said.

Mahler fired one shot into Lenox's abdomen, dropped the gun on his bed and went to their neighbor's house to ask them to call 911, since Mahler and Lenox did not have a telephone, Jewett said.

The sheriff's office received a call from the neighbor shortly after 5:30 p.m.

After being shot, Lenox went outside and collapsed on the front steps, where Contra Costa County sheriff's deputies found him a few minutes later.

He was taken to John Muir Medical Center in Concord where he was pronounced dead.

Responding deputies also found Mahler out in front of his residence with his hands up. He told deputies he had shot Lenox, Jewett said.

Deputies took Mahler to the station where he gave a statement. He was arrested on suspicion of murder and booked into county jail at about 10:45 p.m., Lee said.

Investigators presented their case to the district attorney's office Friday and Mahler was released without charges.

According to Jewett, evidence at the scene corroborated what Mahler had said in his statement. Investigators found the front door broken, fresh holes in the walls, spaghetti spilled on the kitchen floor, old and new holes in Mahler's bedroom door and a bullet hole in Mahler's bedroom floor, Jewett said.