It happened at the Tasker-Morris stop around 6 a.m., transportation authorities told Daily Voice.
The suspect, seen in surveillance footage released by police, approached a woman from behind near the bicycle rack on the mezzanine level, authorities said.
He bumped into her and "a brief altercation ensued," during which the gunman fired a shot before fleeing on foot, police said.
No one was hurt.
Anyone with information on the gunman is asked to call SEPTA Police at 215-580-8111.
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