A man pleaded guilty on Wednesday to killing his mother two days after he completed a 30-year prison sentence for killing a neighbor.

Steven Pratt pleaded guilty to manslaughter for killing Gwendolyn Pratt, 64, at their Atlantic City home in October 2014. An autopsy found that she died from massive blunt-force head injuries.

Pratt was 15 when he shot and killed his next-door neighbor Michael Anderson in an apartment building in 1984. He was tried as an adult and was convicted of murder in 1986.

According to court records, Pratt and Anderson argued after Pratt and some of his friends refused to leave an apartment hallway where they were noisily hanging out. Pratt went back to Anderson's apartment with a lead pipe, but Anderson took the pipe away from Pratt and bloodied his face, the records show.

Pratt then returned with a borrowed handgun and shot Anderson in the face and shoulder, the court records show. Anderson, who Pratt said acted like a father to him, died days after the shooting.

Pratt told a judge through tears after killing his mother that he was guilty and didn't want a trial.

Pratt, 47, must serve 85 percent of a 25-year prison sentence before he'll be eligible for parole.