SEATTLE (AP) — A 4-year-old King County boy found a loaded gun under a mattress and used it to shoot his pregnant mother in the face, authorities said Sunday.

The 27-year-old woman and her boyfriend were watching television in bed Saturday when their son found the gun between the mattress and box spring and unintentionally shot his mother, according to the King County Sheriff’s Office.

The woman, who is eight months pregnant, was taken to a hospital with life-threatening injuries.

The boy’s father told deputies he borrowed the gun for protection. The gun wasn’t reported stolen and is unregistered.

Under Washington’s new state law, Initiative 1639, gun owners could face criminal charges for not safely storing a gun, but it doesn’t go into effect until July.

The case is under investigation.