PRESCOTT VALLEY, Ariz. - A man is in stable condition after he was shot in the back with a handgun by his 7-year-old son, according to police.

Police said the 7-year-old, who has autism, knew where the gun was in a small locked safe in a closet and he knew where the keys were kept.

He moved a dining room chair to the closet in order to reach the safe, after which he removed the gun and shot his dad in the back while he was sleeping, police said.

At the time, the mother was sleeping in the living room with two other sons, a 2-year-old and a 7-year-old. A 13-year-old son was in his room doing homework, according to police.

Police said the boy could not provide a reason for shooting his dad.

The round went through the father's upper chest and back, into the mattress, through the wall, skipping across the floor of the living room and through an exterior wall.

The round did not hurt anyone or damage anything outside the home.

The father was flown by to John C. Lincoln Hospital, where he remains in the ICU.

The incident is still under investigation.

Police said gun owners should consider having a locking device on their guns themselves, rather than just locking them in a safe.

Gun locks are available for free at the Prescott Valley Police Department front lobby.