Update: The two survivors spoke to NBC10 about the shooting. New details here.

A gunman shot two teens on a SEPTA train at the City Hall station Wednesday night, police said.

The ordeal began around 9:45 p.m. when an unidentified suspect on a northbound Broad Street Line train opened fire, shooting a 16-year-old and an 17-year-old, before fleeing the scene.

Responding police officers found the suspect, identified by investigators as Isaac Orsini, 22, on the 1 block of North Broad Street around 10:40 p.m.

Both teens were taken to Hahnemann Hospital and are expected to be OK. The teens also identified Orsini as the suspect, police said.

Orsini was arrested and charged with aggravated assault, simple assault, recklessly endangering another person, and other related offenses.

Officials said surveillance video as well as witnesses helped them capture Orsini.

"This is a great example of how people can help the police solve shootings immediately and the value of technology and video," SEPTA Police Chief Thomas Nestel said.

Police have not yet revealed what led to the shooting.