There was another guy arrested on 11/22/63 under suspicion of killing Tippit but released the same day and never questioned again. Can not find his name right now.
I do not believe Oswald did it. He was on the panic run, I do not think he would stop and kill Tippit the way it was done. If saw police vehicle, I believe Oswald would run away. If he had to fire shots, it would be while he was running away. I do not think Oswald was the guy to stop and fire four shots in the chest of the police officer.