That teen surrendered with his mother on Friday morning. Police say they have not yet recovered the gun.
Another person who was with the 14-year-old at the time of the shooting has been questioned but has not been charged.
The victim, a 19-year-old man, was shot multiple times on a platform at the 15th Street station at about 12:24 p.m. Thursday.
Surveillance video sent to Action News shows a man standing outside a train as two other men exit.
There is a quick exchange of words between the pair and the man on the platform.
According to police, both the 14-year-old and the 19-year-old appear to reach for guns, but only the 14-year-old was able to draw and shoot. The 19-year-old's gun was found nearby, police say.
"I watched the video, he's absolutely the one that fired the gun," said Vanore of the 14-year-old.
Transit police were on patrol at the station and responded immediately, investigators said.
The 19-year-old victim was shot three times: in the chest, stomach and right hand. He was taken to Jefferson University Hospital in critical condition.
The shooter was initially able to escape amid a group of passengers running from the station.
But police say the parents of teenagers, in this case, have been helping police.
"Both the witness and the suspect, both their parents, came in here and were very cooperative, and they're the reason why this case is solved so quickly. So that's what we need, but they got to get involved before this happens because these individuals have guns, they're home, we need to remove those guns from them," said Vanore.
Some riders say they still have concerns
"Why does a 14-year-old have a gun?" asked Geovanni Tanner.
"During that time of day is crazy, but if you're 14 -- imagine what you'll do when you're 18," added another SEPTA rider Friday after learning news of the arrest.
The Philadelphia District Attorney's Office says the 14-year-old will be charged with aggravated and simple assault, among other charges.
Action News is told the hospitalized 19-year-old victim is in police custody.
Anyone with additional information on the shooting is asked to call police.