Multiple media outlets reported the 16-year-old boy died shortly after the leap near Greenville while be was being driven to a psychiatric hospital in Columbia
Coroner Mike Ellis says the teen was restrained on a gurney in the back of a Greenville Hospital Systems ambulance when he loosened his restraints, moved past an emergency technician, opened the door and jumped.
Emergency workers treated the teen before taking him back to the hospital in Greenville, where he was pronounced dead minutes later.
An autopsy was planned Monday.
