PHILADELPHIA — A gunman ambushed a police officer as he sat in his marked cruiser at an intersection, striking him three times in the arm during a barrage of bullets and fleeing before being apprehended, officials said Friday.

Police Commissioner Richard Ross said the suspect fired at least 13 shots at Officer Jessie Hartnett and his car late Thursday. He said the officer returned fire, hitting his attacker at least three times. Hartnett was in stable condition.

“This is absolutely one of the scariest things I’ve ever seen,” Ross said at a news conference early Friday. “This guy tried to execute the police officer. The police officer had no idea he was coming.”