Philadelphia police say an officer is undergoing surgery after he was shot three times in the arm by a man who ambushed him as he sat in his marked police cruiser.

Police Commissioner Richard Ross says the officer returned fire late Thursday night, hitting the suspect at least three times.

Police say the suspect fired a total of 13 shots that hit the officer and his car.

Ross says the shooting was unprovoked. He calls it one of the scariest things he's ever seen.

Both were taken to area hospitals. There's no word on the suspect's condition. The officer is expected to survive.

A motive for the shooting remains unclear.