SAN DIEGO — A road rage incident Friday escalated into a fist fight and ended with one of the combatants pulling out a knife and stealing the other combatant’s car in Mission Valley, San Diego police said. Sometime before 7:40 p.m., the 20-year-old driver of a Subaru Impreza had some sort of encounter with the driver of a blue Honda Civic while driving in the area of Interstate 15 and University Avenue, Officer John Buttle said. The two drivers got out of their cars and fought, Buttle said. They then drove north to Camino Del Rio South west of Interstate 805 and continued the fight.