He is identified as 17-year-old Shane Pryor, who court records show was being held on charges of murder, conspiracy and firearms offenses.
Pryor was in custody for a murder that happened in 2020, and police said at a Wednesday afternoon news conference he had been in custody since he was 14 years old awaiting trial.
Our sister station, 6ABC Action News in Philadelphia, has learned Pryor escaped from the emergency room parking lot at Children's Hospital of Philadelphia shortly before noon on Wednesday.
Two staffers were escorting him after Pryor injured his hand inside the juvenile justice center. It wasn't known how the injury occurred.
He was not shackled when he fled, police said, and it wasn't known whether he was able to get out of his restraints or if he wasn't restrained at all.
Police say Pryor was last seen heading from the area of 34th and Spruce streets to University Avenue and Civic Center Boulevard.
Pryor was last seen wearing a blue sweatshirt, blue sweatpants, socks and slides. Police say he may have since taken off the sweatshirt.
He is 5'7" tall and weighs 180 pounds.
Philadelphia Police news conference on escaped inmate in University City
"We know from our investigation so far, looking at a lot of video, that he was able to go in and out of a few buildings in this area," Deputy Commissioner Frank Vanore told reporters.
Pryor was seen talking to people "asking for a phone ... whatever he could do to leave the area," he said.
Police were searching the buildings and using canines to search large multi-level parking garages, but no lockdowns had been imposed, he said. Officers were also checking the homes of his relatives in other parts of the city, Vanore said.
Defense attorney Paul DiMaio said his client "has always maintained his innocence," even in his initial statement to police. He said a judge in December denied a bid to have the case moved back to juvenile court, which could have something to do with his client's decision to flee.
"He may have felt he wasn't going to get a fair shake," DiMaio said.
Police say Pryor is considered to be dangerous. Anyone with information is asked to call 911.
(Note: Initial details obtained by Action News showed Pryor was being held on several other serious offenses, but police are only confirming the murder, conspiracy and weapons charges).