THE BRONX - Philadelphia police on Thursday arrested the man who stole a gun from an off-duty police officer in Williamsbridge a day earlier.

Authorities say 21-year-old Samuel Thornton walked up to NYPD officer Nilda Quesada Wednesday morning as she was going to her car inside the parking garage of her apartment building on Bronx Boulevard. Thornton allegedly snatched her gold chain from around her neck and demanded her wallet. 

Police say he then punched her in the face and took her purse, which contained her gun.

Quesada was taken to Montefiore Medical Center and is expected to be OK.

Thornton was arrested in Philadelphia at around noon. Police say they used high-tech facial recognition software to identify him. The missing gun, however, was recovered in the Bronx.

Thornton is now awaiting extradition to New York.