PHILADELPHIA (CBS/AP) — An off-duty Philadelphia police officer shot by an assailant has left the hospital.

CBS 3 has learned 46-year-old police Officer Robert Penn was discharged on Monday night.

Penn was getting out of his car at his home when he was shot once, in the right shoulder, early Sunday morning.

Department spokesman Lt. John Stanford said there’s no word on a motive. Stanford said the officer was dressed in street clothes and wasn’t robbed.

Penn told detectives a man walked up to him, muttered a few words and opened fire, then fled.

No arrests have been made in the shooting, but police have interviewed several possible witnesses.

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