The two men walked in around 9:30 p.m. Saturday, demanded money, and walked out.
Police say a man in a light colored sweatshirt walked in, pulled out a silver hand gun and told the clerk, "Give it up".
The thief then cleaned out the cash register while another man looked out.
Both suspects ran out with $400.
Police say one suspect did not have the use of his left arm.
The Citizens Crime Commission is offering a $5,000 reward for information in this case.
The Citizens Crime Commission is also offering a $12,500 reward leading to the arrest and conviction of a man wanted for robbing two other Rite Aid stores.
The incidents happened at the locations on the 4300 block of Richmond Street and the 2500 block of Aramingo Avenue.
In each case, authorities say the man bought an item and left but then returned an hour later armed with a gun and demanding prescription drugs.
If you recognize the robbery suspects contact the Citizens Crime Commission at 215-546-TIPS.