Washington (AFP) – A 19-year-old gunman who shot dead two people on Monday at a St Louis high school had 600 rounds of ammunition and the rapid response by police prevented an even more “horrific scene,” the city police chief said. Orlando Harris, who graduated last year from Central Visual & Performing Arts High School, was killed by police officers who responded swiftly to the attack at the school. St Louis police chief Mike Sack said Harris was armed with an AR-15 style semi-automatic rifle and had multiple magazines of ammunition strapped to his chest and in a bag that he was carrying. “It…