SANTA FE, Texas (AP) — A 17-year-old armed with a shotgun and a pistol opened fire at a Houston-area high school Friday, killing 10 people, most of them students, authorities said. It was the nation's deadliest such attack since the massacre in Florida that gave rise to a campaign by teens for gun control. The suspected shooter, who was in custody on murder charges, also had explosive devices that were found in the school and nearby, said Gov.