Anthony Hall was sitting in the car with his 5-year-old child when he saw the gunman approach 25-year-old Cristina Hopkins on Friday night.
He jumped out of the car and struggled with the gunman.
St. Petersburg police said the gun went off, wounding Almedin Muratovic.
Hall managed to wrestle the gun away from the suspect and threw it out of his reach until officers arrived.
Muratovic was charged with two counts of armed robbery, possession of a controlled substance and possessing a firearm.
Source: The Associated Press