A New Jersey woman shot and killed a friend late Thursday thinking he was an intruder, officials said.

The Mercer County Prosecutor's Office said the victim, Kelvin Watford, apparently was trying to spring a surprise on the woman and was on the phone with her when he was shot once in the chest.

At 11:23 p.m., a woman called 911 to report she had shot an intruder she saw at the bottom of the stairs of her Hamilton home but then reported the fatally wounded man was a friend, the office said in a statement.

Watford, of Willingboro, was pronounced dead at the scene.

Officials said the preliminary investigation showed that the woman, whose name was not released, was on the phone with Watford, who told her he was returning from a trip but not in the immediate area.

"As she continued to talk to Watford on the phone, she heard a dog barking and noises outside of her house," the statement said. "The noises outside of her house continued and she retrieved her gun.

"She heard someone inside of her house and walked to her bedroom door, still on the phone. She then opened her bedroom door, observed the shadow of a person in the dark on the stairs, and fired one gunshot."

Police said the shooting appears to be an accident but the investigation is not yet closed.