An Army psychiatrist set to be shipped overseas opened fire at the Fort Hood Army post Thursday, authorities said, a rampage that killed 12 people and left 31 wounded in the worst mass shooting ever at a military base in the United States.The gunman, first said to have been killed, was wounded but alive in a hospital under military guard, said Lt. Gen. Bob Cone at Fort Hood. He was shot four times, and was on a ventilator and unconscious, according to military officials. "I would say his death is not imminent," Cone said.The man was identified as Maj. Nidal...