Just as opening statements in his trial were about to begin, a Marietta man pleaded guilty Tuesday to murdering Christopher Reynolds when he tried to break up a domestic fight between the killer and his girlfriend.

Charles Renard Mahaffey, 26, was sentenced to life in prison after admitting he fatally stabbed Reynolds, on Nov. 25. Mahaffey also pleaded guilty to aggravated assault.

Reynolds, 26, interceded in an argument Mchaffey and his girlfriend were having outside a house on Brackett Drive. Mchaffey stabbed the unarmed Reynolds once in the abdomen and once in the throat.

At first Mchaffey said a stranger attacked Reynolds. But the hunting knife that was used had blood from both Reynolds and from Mahaffey, who cut himself during the attack.

Then Mchaffey tried to claim self-defense when he was confronted with statements from witnesses, deputy chief assistant district attorney Jesse Evans said.

“This was a devastating loss for the victim’s family,” Deputy Chief Evans said. Mchaffey must serve at least 30 years in prison before he will be eligible for parole.