WPVI-TV reports the two male and two female victims were on a basketball court in Chester when possibly two suspects fired from a bridge. It happened around 6 p.m. local time on Saturday.
The victims, who are in their teens and 20s, were taken to a local hospital. They are in stable condition and their injuries aren't considered life-threatening, AP reported.
Police say about 30 people were on the basketball court when the shooting happened.