LONGMONT, Colo., June 28 (UPI) -- A 12-year-old boy was killed Sunday when stomped on by a bull that threw him while he was competing in a rodeo in Colorado, authorities said.Boulder County Sheriff's Deputy Cathy Bryarly said the youth was tossed from the bull's back before he completed the 6-second ride and the animal's rear legs came down on his lower abdomen, missing a protective vest he was wearing, the Longmont Times-Call reported.