PHILADELPHIA (WPVI) -- A suspect is in custody after a shooting on a SEPTA train at 52nd and Market streets on Friday morning.
The shooting happened just before 8 a.m. on the Market-Frankford Line train at the 52nd Street station.
It started as a fight between two men and quickly escalated when two more men got involved.
"Erupting into a full-blown three-on-one assault. One of those individuals produced a handgun, firing a round, striking one of the assailants in the arm," said Chuck Lawson, the acting SEPTA police chief.
It is not clear what led up to the shooting, but dramatic video showed a scuffle on board the train before you hear the shot.
Minutes later, you hear panicked passengers at the 52nd Street Station worried for their lives as another man stands holding a gun.
A group of people can be seen holding the suspected shooter down on the platform while officers run up to the scene. Police confirmed late Friday afternoon that the person shot was one of the people holding the shooter down until police arrived.
One of the officers recovered a gun and is seen unloading it. The suspect is then handcuffed and carried away. All three people believed to be involved in the initial fight were detained. Police are searching for a fourth person.
The 19-year-old victim was shot once in the arm and is expected to recover.