Sheriff's investigators in north Florida were trying to determine how a 4-year-old boy got his hands on the gun he used to shoot his mother as she drove a pickup truck.

Putnam County Sheriff's Office spokesman Joseph Wells says 31-year-old Jamie Gilt of Jacksonville owns the .45-caliber gun the boy fired Tuesday afternoon.

A deputy saw her behaving frantically inside the truck, which was stopped partially in the road.

The deputy then saw she'd been shot in the back and the bullet had exited from her stomach area.

Wells says Gilt told deputies her son had accidentally shot her. He says she was taken to a hospital and was in stable condition.

The boy, who wasn't injured, is with relatives. The Florida Department of Children and Families is also investigating.