Passengers fled a SEPTA bus in Center City Philadelphia overnight after gunshots rang out inside the vehicle, according to police.

The shooting happened around 1 a.m. Thursday on the Broad Street Line Nite Owl bus, which was approaching Chestnut Street. The Nite Owl bus fills in for the Broad Street Line subway when it’s closed overnight.

The bus driver told police he heard three to four gunshots from the back of the bus. About 15 passengers rushed toward the front of the vehicle and fled, the driver told police.

The victim, a 29-year-old man, was shot in the chest and taken to Thomas Jefferson University Hospital in critical condition, according to SEPTA.

“The shooting happened on the bus, inside the bus. We found one spent shell casing on the floor in the rear of the bus,” Philadelphia Police Chief Inspector Scott Small told reporters. “We also found a loaded magazine — a clip — also on the floor in the rear of the bus.”

Small said the shooter fled with the other passengers, but told reporters he’s “pretty positive” that cameras on the bus recorded the shooting. He also said it was likely security cameras on buildings in Center City captured the shooter leaving the bus.

“Nobody stayed this time to act as a witness,” Small said.

Central Detectives are investigating the shooting along with SEPTA police.