Person shot on SEPTA's Market-Frankford Line in West Philadelphia

PHILADELPHIA (CBS) -- In less than a week, there have been two shootings involving SEPTA causing riders to worry about their safety. It was a chaotic Friday morning for some in West Philadelphia after a shooting aboard a SEPTA Market-Frankford Line train.

Police say three suspects are detained and facing charges of aggravated assault. It took the police less than five minutes to respond.

SEPTA told CBS News Philadelphia that a person was shot on the train at 52nd Street Station. SEPTA police say four people were involved although you can only see three on the video.

The victim is a 19-year-old who was shot once in the left arm, Philadelphia police said. He is in stable condition at Penn Presbyterian Medical Center.

A video taken by a witness Mark Krull on the platform shows a person on the ground being restrained by officers.

"The individual who was shot subsequently held on to the shooter until police arrived, subsequently detaining three of the four individuals involved," acting chief SEPTA police Charles Lawson said.

"There are issues here that are much bigger than SEPTA, particularly more and more people going straight to their guns if they hear of feel disrespected," SEPTA general manager Leslie Richards said.

Lisa Jones, a SEPTA rider, said people need to find nonviolent solutions to problems.

"People have bad tempers, and people do not want to take time to talk something out, the first thing you do is go for a weapon," Jones said. "And I've seen people on that train get upset over nothing. Instead of being able to walk away, they fight or they bring out a weapon. It's stupid, and it causes problems for everybody else."

Police activity was causing delays on the Market-Frankford Line, but service was resuming around 10 a.m.

Philadelphia police are leading the investigation. They're looking still looking for the fourth suspect.

In:
• SEPTA
• Pennsylvania
• Gun Violence
• Philadelphia