Investigators say a medium-sized black man walked into the Supermercado La Mexicana store off Veterans Memorial Highway at about 7:30 p.m. and walked around the shop for a few minutes.
According to police, he took an item off the shelf and headed toward the cash register, where he acted as though he was going to pay for it.
Instead, police say he pulled out a handgun and pointed it at the woman behind the counter, demanding she give him cash from the register.
The employee handed him an undisclosed amount of cash, and police say he fled the scene on foot.
Police say the suspect was last seen wearing a gray long-sleeve shirt, gray pants, a black undershirt, glasses and a gray knit cap.
Anyone with information is asked to call investigators at (770) 499-3945.