It happened at the Julia De Burgos Elementary School at 4th Street and Lehigh Avenue just after 11 p.m. Tuesday.
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Investigators tell Action News the victim and the gunman were arguing and that escalated into gunfire.
The 26-year-old victim was shot four times. He was taken to Temple University Hospital in critical condition.
Police say the gunman was last seen running across Lehigh Avenue into a park.
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Authorities say they will be looking at surveillance cameras in the area.
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