By ACACIA CORONADO and JIM VERTUNO UVALDE, Texas (AP) — An 18-year-old gunman killed 19 children as he went from classroom to classroom at a Texas elementary school in a rampage that also left two adults dead, officials said, adding to a gruesome, yearslong series of mass killings at churches, schools and stores. The attacker was killed by a Border Patrol agent who rushed into the school without waiting