SAN FRANCISCO—Federal prosecutors charged a San Francisco man who was identified as having returned fire at an armed attacker outside of a liquor store with illegal ammunition-possession, according to the report by the Mercury News published on October 1.

The court records say Gregory Mack was charged with possession of ammunition, and he would be sentenced to a maximum of 10 years in prison and a $250,000 fine. Police found two guns and a “drum” style magazine, designed to hold extra bullets, during the investigation conducted two weeks after the incident. Police served a search warrant at Mack’s house.

Mack bumped into an alleged gang, whom Mack describes as his rival, outside of liquor shop called Rubins Market in San Francisco in April, according to the complaint. The man fired at Mack, and then Mack returned that fire. As a result, an innocent bystander was shot in his leg by a fire shot by the other man, authorities said to the Mercury News.

Federal prosecutors saw a surveillance video and said that Mack had brought a loaded firearm, and “retrieved what appears to be a firearm from his waistband and put it in his right jacket pocket.”

According to the court records, Mack was not allowed to possess ammunition because he had a criminal history of robbery when he was a teenager, as well as ammunition possession conviction six years ago.