Shane Pryor, 17, fled from the Children's Hospital of Philadelphia (CHOP) emergency room parking lot at 34th & Spruce streets just before noon, said PPD.
6abc reports he was being held on murder, conspiracy, and firearms offenses.
He was last seen headed toward University Avenue and Civic Center Boulevard, the department said. Pryor was wearing a blue sweater, blue sweatpants, and no shoes.
He is described as 5-foot-7 and 180 pounds.
Anyone who spots him should call 911, they added.
(Note: This story has been edited for clarity.)
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