The incident occurred just after 1 p.m. on the 4800 block of Market Street near a Forman Mills department store.
Police say someone working on a demo project on that block double parked and left their keys in the engine. That's when the 16-year-old male jumped in the car and took off.
Several men from the work site then jumped into a white vehicle and chased after the stolen vehicle.
The teen in the stolen vehicle got into an accident with an innocent person driving a blue SUV, officials say.
The guys in the white vehicle then got out and chased the teen near 48th and Market streets, where the teen was stabbed twice in the back, allegedly by the people chasing him.
A gunshot was also fired at the scene, police say. It is still unclear who fired the shot.
The teen ran into Forman Mills with blood on him, and someone called 911.
The teen was transported to Penn Presbyterian Medical Center and listed in stable condition.
He is currently being held in custody, police say.
So far, no weapon has been recovered from the scene.