Police say a suspect described as a white male, 20 to 30 years old, followed two senior citizens to their car.
He then forced them at knifepoint to drive to a series of bank ATMs. $500 in cash was taken.
They then returned to the Walmart lot and the bandit fled on foot.
"There are two people instead of one, which is a little on the brazen side. Usually you might see one victim in a robbery," Philadelphia Police Sgt. Dennis Rosenbaum said.
The bustling malls and the parking lots become inviting targets for stickup men, pickpockets, and vehicle burglars. Police say to be on your toes at all times.
They say alert police and the other security personnel if you see something suspicious.
Walmart and owners of the Franklin Mills Mall say they have now increased security and city police patrols because of the holiday season.
The suspect remains at large.