The man was doing some late-night shopping at the Dollar General store on Dunn Avenue when all of the sudden, two men stormed in and tried robbing it.
Unfortunately for one of them, the man happens to have a concealed weapons permit, and Lt. Rob Schoonover with the Jacksonville Sheriff's Office says the man wasted no time springing into action.
"There was a citizen who had a concealed firearms permit that was inside the store as a customer," says Lt. Schoonover. "He fired at the suspect, striking him and killing him."
The other robber ended up getting away -- he is described by police as a black male about 6 feet tall and wearing a blue bandana. He drove off in a small SUV.
There are no charges pending against the customer.