An Atlanta man charged with murder twice in two years has been found guilty of a lesser crime in the first case, Fulton County officials announced Friday.

Dontavis Montgomery, 21, stabbed Nicholas Roberts in the back during a fistfight in January 2015, according to a news release from the district attorney's office. He was found guilty of charges including involuntary manslaughter and aggravated assault.

The fight broke out after Montgomery’s half-brother started smoking a cigarette in Roberts’ southwest Atlanta living room; Roberts had asked him not to smoke because his 11-year-old daughter has asthma.

Roberts’ wife and her friend tried to stop the fight, but Montgomery grabbed a kitchen knife and punctured Roberts’ lung, the news release said.

After fleeing, Montgomery turned himself in six days later, claiming he’d stabbed Roberts in defense of others.

He was released on $100,000 bond in October 2015. A year later, he was arrested and charged in the murder of his 15-year-old cousin, Marquez Montgomery.

Dontavis Montgomery said the shooting was an accident.

That case is still pending.

In Roberts’ death, Judge Todd Markel sentenced the defendant to 20 years in prison.

The attorneys listed for Dontavis Montgomery did not answers call Friday afternoon.

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The 21-year-old is accused of killing his cousin while out on bond for another murder.