It happened around 1:15 a.m. on the 1700 block of Saints Paul Street in the Nicetown section of the city.
Philadelphia police found the 55-year-old with a gunshot wound to the chest.
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"According to a witness who was with the victim, she said he was sitting on a bench at the park. She left him to go to a store to get some food and when she returned she heard one gunshot," Philadelphia Police Chief Inspector Scott Small said.
Small said the shooting happened at the park, but the victim was able to walk a half a block before collapsing.
He was taken by police to Temple University Hospital in critical condition.
No arrests have been made.
Small said there are no cameras at the park.
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