The incident happened Monday at Allegheny Station in Philadelphia's Kensington neighborhood.
SEPTA officials said the man had been caught evading the fare and was being escorted off the property when the incident occurred.
In a statement, a SEPTA spokesperson said the agency opened an Internal Affairs investigation immediately after the incident.
"An Internal Affairs investigation was opened right after the incident, and because of that, we have to defer at this time on commenting further," the spokesperson said. "We will share results of the investigation publicly when it concludes."
According to SEPTA, no injuries were reported.