A 15-year-old boy accidentally shot and killed himself while playing with a loaded gun at a friend's house Wednesday evening, police on Long Island said.

Three teens were playing with the gun inside a Williams Street home in Glen Cove when one of them fired a shot, hitting himself, Nassau County police say.

The boy, identified by relatives as Derek Cosme, was pronounced dead at the scene.

Cosme's mother and aunt were on their way to pick up the teen from his friend's house when they learned he was dead, another aunt, Rosa Vasquez, told News 4.

Cosme was heading into the 11th grade at Glen Cove High School and was described by his aunt as a good kid who never got into trouble and loved music.

Derek had four sisters whom "he adored and loved so much," according to older sister Jasmine.

"He was very outgoing, friendly, smart just loved by so many," she wrote on a fundraising page for funeral services.

Police say a retired county corrections officer lived in the home where the boy shot himself, and the gun was owned by a licensed pistol holder.

Vasquez says the gun should have been locked up and an adult must be held responsible. She said the family would not stop until they got answers.

Neighbor Aleka Bellidoro said, "I'm very shaken up. Even though I'm not close with them, I've seen them outside, I've talked to their grandmother."

"I'm shocked," said Frank Ecker. "I've lived here for 20 years, never seen anything like this."

The investigation is continuing.