The incident happened just before 10 p.m. at a Subway restaurant on Glenmere Lane on May 29.
Authorities say the suspect, who was carrying a metal pipe, demanded money from an employee behind the counter and took off with an undetermined amount of cash.
Police are offering a reward for information leading to an arrest.
The suspect was described as a white male with short dark hair and a medium build. He was wearing tan pants and a dark gray button-down shirt with a black tee shirt underneath.
Anyone with information is asked to call police.