A foot chase ensued, weapons were drawn and a shot was fired.
A 21-year old man was wounded and transported to Crozer Chester Medical Center where he later died from his injuries.
Eyewitness Jamiel Torres lives across the street from the shooting, and says he watched as police chased the victim.
"I saw the boy running. He went behind the house, and the cop told him to stop or I'll shoot, and he just shot him in the back," tells Torres.
The victim was shot behind an apartment building. He was rushed to Crozer Chester Medical Center.
The Delaware County District Attorney's office says a fight broke out at the hospital and Chester Police called for county-wide assistance.
Police responded to the hospital, and soon calm was restored.
Resident Jamie Lee said she was in her backyard when the gunfire erupted.
"The boy had just walked past, and it was no more than 10 minutes, and the next thing I know, we heard gunshots. And I jumped up and went out front, and the cops had shot the boy. He had just walked passed my house. He wasn't doing anything," said Jamie Lee.
Multiple sources say the victim had a gun on him.
Police say a weapon was recovered at the scene and submitted into evidence.
The name of the officer and the name of the victim have not been released.
The incident is being investigated by the Delaware County Special Prosecutor's Office.
Anyone with information regarding the incident can contact Detective Lythgoe at 610-891-4243 or Detective Worrilow at 610-891-4244.