An Army psychiatrist opened fire Thursday at Fort Hood, Texas, killing at least 11 people and wounding 31 others before being shot to death, military officials said.

NBC News’ Pete Williams reported that U.S. officials identified the gunman as Maj. Nidal Malik Hasan, an Army psychiatrist who had been promoted to major in May. A defense official told NBC News that Hasan arrived at Fort Hood in July for his first assignment after completing his psychiatry residency at Walter Reed Army Medical Center in Washington, followed by a course in disaster and preventive psychiatry.

Hasan, who was 39 or 40, was scheduled to be deployed to Iraq on Nov. 28, officials said. Sen. Kay Bailey Hutchison, R-Texas, said military officials had told her that Hasan was “pretty upset” about his deployment orders.