A 4-year-old Vernal boy remains in the hospital after he climbed a shelf, found a loaded handgun and accidentally shot himself in the chest Thursday.

The boy was transported to Ashley Regional Medical Center in critical condition, according to a Uintah County Sheriff’s Office news release. He was soon flown to a hospital in Salt Lake City.

On Thursday night his condition was upgraded, police say.

According to the release, the boy climbed up a set of shelves in a bedroom closet and found the gun. Adults were in the home at the time, and emergency responders arrived at the house within minutes.

The accident is under investigation.