The shooting happened November 30 in the 4600 block of East Roosevelt Boulevard in the city's Summerdale section.
RELATED: GameStop manager, 20, shot during attempted robbery in Philadelphia, police say
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Cameras captured one of the men walking into the store and immediately going toward the counter, where the 20-year-old victim had just ducked to trigger the alarm.
The suspect then shot the victim once in the leg before all three escaped in a Ford pick-up truck.
The store's alarm was activated and nothing was stolen.
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Police believe the gunman meant to rob the GameStop, but panicked, possibly after seeing the manager press the alarm.
Anyone with any information is asked to call the police at 215-686-TIPS.