A 19-year-old man who authorities believe fatally shot a teenage boy Friday told deputies he thought the gun was empty when he pulled the trigger inside a home on the northwest side, according to court documents.

The man said he was in his upstairs bedroom clearing ammunition out of an AK-47 rifle in the home in the 8000 block of North Country Home Lane, north of Cortaro Farms Road, when the incident happened, according to a search warrant filed by the Sheriff’s Department in Pima County Superior Court.

He took out the rifle’s magazine and believed the gun was empty when he pulled the trigger, firing a single shot that struck Luis Angel Lopez Jr., 17, who was in the adjacent den area, the warrant said.

The man went to check on Lopez and tried to render aid, grabbing a towel to cover his wound, according to the warrant.

Deputies say they found Lopez on the couch with the towel behind his head. He was pronounced dead at the scene.

Deputies reported there were suspected explosive devices inside the home and called in the Pima Regional Bomb Squad and Bureau of Alcohol, Tobacco, Firearms and Explosives to remove them.