ROCHESTER, Minn. – A fight broke out with shots being fired at a teen-age birthday party at the Graham Arena complex on the Rochester fairgrounds. No one was injured. The combatants dispersed as police arrived. But already, witnesses said, three shots had been fired. Officers didn’t find any shell casings. It appeared, though, that one bullet punctured the radiator of a Volkswagen Jetta. This was about 10 p.m. at a quinceanera, a traditional Mexican celebration for girls on their 15th birthday. Space had been reserved for the arty. Police said the fight involved youths 15 to 20 years old. They believe there was a single shooter.