It happened around 10:15 p.m. in Campbell Square Park located at Allegheny Avenue and Belgrade Street.
Police said Anthony Cheever, 19, 0f the 3500 block of Decatur Street, was shot in the chest, He was taken to Hahnemann University Hospital where he later died.
Officials said a 16-year-old boy was shot in the leg. He was taken by police to St. Christopher's Hospital where he is in stable condition.
Investigators said the shooter or shooters fired at least four shots at a group of at least 25 teens who were gathered in the park.
Officials said they believe an argument led to the shooting.
Police took several witnesses to speak with homicide detectives.
"Those witnesses were able to give us a description, but we're getting many descriptions," said Philadelphia Police Chief Inspector Scott Small. "We're getting information that the shooter or some of the people with the shooter fled on foot. We're also getting information that people with the shooters may have been on bicycles and left the scene."
As neighbors walked through the park early Thursday morning, they said they were shocked by what had transpired there the night before.
"I can't believe it was two kids," said Erica Borroro. "It's crazy."
Long-time Port Richmond resident Larry Lorch added, "There's no value today on life. It's just a shame. They are young. They don't realize (they took) somebody's life, their future, everything."
Police said one or more of the shooters might have been wearing ankle monitors. If so, police said they will be checking with officials in probation and parole to try and track down those monitors and find the shooters.