Pittsburgh Fire, EMS and Police responded to the 1200 block of Oakglen Street for a report of a male injured in a backyard fire around 10:45 p.m.
A 34-year-old male appears to have poured a large container of gasoline on a fire in a fire pit when there was an explosion.
An off-duty medic who heard the explosion ran to the scene and rendered aid until more help arrived. The man was transported to a local hospital in critical condition with burns over 75 percent of his body.
The Fire Investigation Unit, made up of investigators from the Pittsburgh Bureau of Fire and detectives from the Pittsburgh Bureau of Police, are investigating.