A man opened fire Monday on a cashier at a supermarket in DeKalb County, Georgia, after an argument about masks, killing the woman and injuring a DeKalb County Sheriff’s Office reserve unit deputy who returned fire. The suspect was hit by the deputy and hospitalized, said Sheriff Melody Maddox at a news conference. Several shoppers were inside the Big Bear Supermarket when the shooting occurred, Maddox said. 11Alive reports the supermarket has a sign posted requiring a mask for service. The argument was “in reference to wearing a mask,” Maddox said. The deputy, who was working part-time as security for the supermarket, tried to intervene and returned fire, hitting the suspect a few times after he fatally shot the cashier. The deputy was also reportedly struck twice but had a bulletproof vest on. His condition is stable, the sheriff said.