By Scott Morgan and Joseph Ax PERRY, Iowa (Reuters) -A sixth-grade student was killed on Thursday morning and five other people wounded when a 17-year-old opened fire at an Iowa school on the first day of classes following the winter break, law enforcement officials said. The suspect was identified as Dylan Butler, a student at Perry High School, officials said at a news briefing. He was found dead with an apparent self-inflicted gunshot wound by responding officers. Police also discovered an improvised explosive device when searching the high school, Mitch Mortvedt, an assistant director with…