A North Amityville man fatally shot his mother’s boyfriend Tuesday after the two men tussled, a Suffolk prosecutor said Wednesday.

Tephonte Smith, 18, entered a not-guilty plea to second-degree murder in First District Court in Central Islip. Authorities said Smith killed Rashad Woolridge, 28, in their Avon Drive home about 12:40 p.m. in an apparent domestic dispute.

Woolridge’s body was found in the home’s basement; he was pronounced dead at the scene.

Assistant District Attorney Laura Newcombe said Woolridge and Smith’s mother, Stephanie Sims, argued about noon and Smith got involved.

Smith and Woolridge got into a scuffle and the two had to be separated, Newcombe said. Both men went outside, she said.

Shortly after, Smith went down to the basement, where his bedroom is located, and Woolridge followed minutes later, Newcombe said.

advertisement | advertise on newsday

In court papers, Sims, 33, said she heard Woolridge yell in the basement, “Where you at, Tephonte?”

Then she heard a shot, Sims said.

“I ran downstairs and saw Rashad lying facedown on the floor,” she said in the statement to police.

Sims said she called 911.

Smith left the house after the shooting, Newcombe said. He surrendered to police later on Tuesday with his family and pastor, his attorney said. Three children were in the home at the time, Newcombe said.

Newcombe said “there was a handgun found in the victim’s hand” when his body was flipped over.

Woolridge’s wounds were consistent with being shot by a 12-gauge shotgun with his head “turned away when he was shot,” she said. A 12-gauge shotgun was found next to Woolridge’s body, she said.

Newcombe said Smith was arrested Sunday on unrelated charges of resisting arrest and two counts of harassing a police officer.

Suffolk County District Court Judge Toni A. Bean set Smith’s bail at $50,000 cash or $100,000 bond.

Smith’s attorney, George Duncan of Central Islip, said his client is a 2016 Amityville High School graduate and “a fine young gentleman, active in the church.”

advertisement | advertise on newsday

Duncan added, “It seems like the facts and circumstances may support a self-defense claim.”