A teen accidentally shot and killed himself as he horsed around with a loaded handgun Wednesday night on Long Island, police said.

The 15-year-old was was playing around with two pals in a Glen Cove home when the gun went off, cops said.

The boy, who was pronounced dead at the scene, was identified by relatives as Derek Cosme, a junior at Glen Cove High School, according to The Long Island Herald.

The boy did not live in the home but the gun belonged to a licensed pistol holder who did, Nassau County Police spokesman Vincent Garcia said.

A grandmother who resides in the home was a former Nassau County corrections officer, detectives said.

Police say they are investigating the incident.