A teenager being held on Johnathan Walkermurder charges who slipped away from prison staff in Philadelphia was still on the run Thursday as police warned he was considered dangerous.

Shane Pryor, 17, was being taken to a children's hospital in Philadelphia for treatment for an injury to his hand on Wednesday at about noon when he escaped and fled, Philadelphia Deputy Commissioner Frank Vanore said at a news conference.

"When staff pulled up into the drive of Children's Hospital we know now through video evidence, as the male was exiting that car, he was able to escape from staff and run from this area on foot," Vanore said.

Pryor was not shackled when he exited the vehicle he was being transported in, but Vanore said it wasn't clear whether he had been shackled during transport.

The U.S. Marshals Service in Philadelphia later said Pryor may be driving a stolen Ford F-150 with Pennsylvania license plate ZTS-0503.

Here's what we know:

Where was the escaped prisoner last seen?

Vanore said Wednesday that security cameras showed that Pryor "ran building to building" after fleeing from the hospital parking lot and has asked people he encountered for a phone. Police were searching those areas, including a large parking garages.

He was wearing a dark blue sweatsuit, socks and slides, but Vanore said he may have discarded the sweatshirt at some point and was wearing a blue T-shirt underneath. Pryor is Black, 180 lbs, 5-foot-7 and had braids in his hair, police said.

Pryor was last seen in the area of the children's hospital, near University Avenue and Civic Center Boulevard, police said in a post on social media.

"We don't think he's in the hospital area at all," Vanore said. "In this case, we need the public's help. If somebody may know where the individual is."

Police spokesperson Miguel Torres told USA TODAY on Thursday morning there wasn't new information about whether there had been additional sightings.

What was he in prison for?

Pennsylvania court records show Pryor was charged with murder, conspiracy, reckless endangerment and several firearms offenses. The charges date back to 2020, and Vanore said Pryor was still awaiting trial in custody at a juvenile facility. He had not been convicted of the crimes at the time of his escape.

"He's been in custody since he was 14 years of age," Vanore said.

Torres told USA TODAY in an email Thursday that Pryor was charged in the Oct. 10, 2020, death of 54-year-old Tanya Harris of Philadelphia, who had been shot in the head and was found in an alley. Pryor was arrested Oct. 15, 2020. Police didn't say how investigators connected Pryor to the shooting.

Last September, another Pennsylvania inmate who had been sentenced to life for murder drew national attention when he escaped from a state facility in Chester by crab-walking up walls in an exercise yard and evaded law enforcement for nearly two weeks before being recaptured. That search drew hundreds of officers and search dogs and set residents on edge as they locked down in their homes.

Vanore said there were no lockdowns in place as of Wednesday afternoon.