The incident happened around 1:30 p.m. at the Empire Smoke Shop on the 1400 block of Chester Pike in Crum Lynne, Pa.
Police say, when they arrived, they found the employee behind the counter and shot numerous times.
Authorities have released an image of the suspect believed to be involved in the shooting. The suspect should be considered armed and dangerous.
Anyone with information is asked to contact the Ridley Township Detective Division at 610-532-4000.