It happened at 7:45 a.m. Monday in the 300 block of 8th Street, just blocks away from Chester High School.
Police say a 20-year-old and two 15-year-olds were shot.
At this point, investigators believe this was a drive-by shooting, and say the victims may have been innocent victims.
Witnesses say a car drove up the street and a gunman opened fire, shooting several times, into a crowd of young people congregating in front of a vacant building.
One 15-year-old was shot in the forearm while the other was shot in the wrist. The 20-year-old suffered a graze wound to the head.
The victims ran to the home of Mark Brice for help.
"I let them in, I set them down on my furniture, I took off my shirt, wrapped it on his arms and I said 'just relax, calm down, I called 911,'" Brice said.
All three victims were taken to Crozer Chester Medical Center in good condition.
Police said there has not been any recent trouble among students in the Chester-Upland School District, so they're trying to figure out a motive.
Police are also asking for help from neighbors. So far, they say, witnesses have not been forthcoming with information or a description of the car or the gunman.