Earlier Thursday, police told Action News it wouldn't be long before they expected to have the gunman in custody, thanks to SEPTA's state-of-the-art surveillance system.
"This is not going to be an unsolved crime. This is going to be solved, and it's going to be solved quickly," said SEPTA Transit Police Chief Thomas Nestel.
That's because, police say, the shooting was captured in crystal clear video by SEPTA's surveillance cameras. They are everywhere.
Wednesday afternoon, a fight among students erupted inside a subway car near the Susquehanna stop. Police say the cameras recorded the gunman's every move.
"The offender exited the train, turned around, and fired into the train," said Nestel.
Bullets struck a 17-year-old boy in the arm and a 14-year-old boy in the leg. On Thursday police took that video to schools in the area, asking staff to help them identify the gunman.
"The shooter made a serious mistake yesterday shooting at someone. But he really made a mistake by shooting someone on SEPTA property."
Police say if you commit a crime on a SEPTA train, you will get caught. Each train car is equipped with ten cameras, and each station has anywhere from 15 to 50 cameras.
Every weekday, SEPTA police overlap shifts to allow for extra patrols in the afterschool hours. They always stay in close contact with the school district, so they know if school-related problems are headed their way.
SEPTA riders said Wednesday's shooting made them uneasy. But it won't change when or where they ride the SEPTA rails.
"Just one of those things," said Thomas Howard of North Philadelphia. "Something that can happen any time. It's not going to stop me from riding the subway."
"You have to be aware of your surroundings everywhere you go," said Charles Crowder of Center City, "because there is so much violence around."
Police are not releasing that surveillance video because they say it is so good they don't need the public's help identifying the shooter. They don't think it will be long before the gunman's in custody.
Also Thursday, the 17-year-old victim was released from the hospital. The 14 year old will remain hospitalized. The bullet went into his hip and lodged in his stomach.