The incident occurred on an inbound Norristown High Speed Line train at Villanova Station around 10:30 p.m., SEPTA spokesperson Kelly Greene said.
"The male suspect got off the train and kicked the door," Greene said. "He then showed a gun and tapped it on the glass before running away."
A statement from Villanova officials says the suspect got off at the Aldwyn Station and then running across a pedestrian bridge.
A search for the suspect came up short Tuesday evening. Additional police presence was expected at the university.
Click here to follow Daily Voice West Chester and receive free news updates.