Official say a man walked into the convenience store located in the 700 block of North Euclid Street on Thursday and demanded money from the clerk.
The clerk said before he knew what was happening, the suspect pulled out a gun and hit him over the head. That's when the gun went off.
The suspect then turned to a second clerk who handed over an undetermined amount of cash.
Shortly after, police say the armed robber met another man outside, who they believe was a lookout.