A shootout happened around 10:30 p.m. on the 2100 block of North 28th Street in Strawberry Mansion.
Police say gunmen targeted a home, striking a 17-year-old male in his abdomen. A bullet grazed his head and another grazed his arm.
Police say the shots continued, not only from outside the home, but from inside as well.
"There are several spent shell casings inside that home, which indicates there was return fire from that home onto the street directed at the shooters that were shooting at the home," Philadelphia Police Inspector D.F. Pace said.
The shooters fled on foot and are still on the loose.
The teen was taken to the hospital in stable condition.
Police say he was alone in the home at the time.
Thirteen of the 21 shots fired hit a home next door that was not the target, police say. Nobody in that home was injured.
Earlier in the evening, around 8 p.m., a shooting in the 2900 block of West Gordon Street wounded a 15-year-old male and a 30-year-old man.
The 15-year-old was shot in the back and taken to the hospital in stable condition.
The 30-year-old was struck in the leg. His condition was not released.
The scene of the double shooting is just two and a half blocks from where the 17-year-old was wounded in the shootout hours later.
No arrests have been made.