The fire destroyed the Nowata Firearms Range on Highway 60 west of Nowata.
Sam Schafnit with the fire marshal's office says a projectile was shot down range and hit the backstop which was made of a rubberized material starting the fire.
The fire was reported just after 2 p.m. destroyed the building. Fire officials say a Nowata customer, 66-year-old Leslie Hazin, ran back inside to get his gun and died in the fire.
The Bureau of Alcohol, Tobacco and Firearms is still investigating the fire.
3/12/2015 Related Story: 1 Dead After Fire Erupts At Nowata Gun Range