According to authorities, a woman was robbed at gunpoint around 8:40 p.m. Friday at 22nd and Somerset streets.
Police responded, and while searching the area, they encountered a 17-year-old boy who fit the description of the suspect.
While patting the teen down, police said they felt a gun in his waistband.
Police said the teen reached for the weapon and a struggle ensued.
An officer then discharged his gun three times, striking the teen.
"We believe twice in the leg and once in the lower back. Recovered from that male was a revolver," Philadelphia Police Department spokesperson Staff Inspector Sekou Kinebrew said.
Kinebrew said it's looking like the teen was not involved in the initial robbery.
"At this point we're uncertain if this is the person that committed that robbery. At this point, to be completely accurate, we don't believe it's the person that committed the robbery, but all of that is still under investigation," Kinebrew said.
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The teen was taken to Temple University Hospital by police. He's listed in critical but stable condition.
Philadelphia's new police commissioner Danielle Outlaw was at the scene as officers investigated.