(CNN) – A controversy over the use Mask Decollep County Sheriff Melody Maddox said an employee was killed and two others, including an officer, were injured in a shooting at a grocery store on Monday.

The suspect entered the Big Bear supermarket at South DeColp Mall in Decatur, Atlanta, where he had an argument with the cashier about the mask. Maddox gave some details about the argument, but said it was for a mask.

The suspect then shot the employee, and he died of his injuries, Maddox told a news conference Monday.

Aerial view of the Big Bear supermarket in Decatur, Georgia, where an employee was shot dead Monday.

A reserve agent who was on security duty at the store shot the suspect. Both were injured and taken to local hospitals.

Maddox said the Reserve Agent was a 30-year veteran before retiring and joining the Reserve Division. He is in a stable condition.

The incident is being investigated by the Georgia Bureau of Investigation and Decalf County Police.