Nov. 6 (Bloomberg) -- An Army psychiatrist is under guard in a Texas hospital after being accused of killing 13 people and wounding 30 others in what officials say they believe is the worst mass shooting at a U.S. military base.

Major Nidal Malik Hasan, 39, opened fire on fellow soldiers with two handguns at the Fort Hood Army Base yesterday before he was shot several times, Lieutenant General Robert Cone, the commander of III Corps at the base, told reporters. Hasan was shot by a female civilian police officer, the Army said.

“This is a tough one,” General George Casey, the Army’s chief of staff, told reporters at Fort Hood this afternoon. “It is a kick in the gut. There’s no doubt about it.”

Cone said Hasan is in custody and in stable condition.

Military officials and the Federal Bureau of Investigation are probing what triggered the attack at Fort Hood by the licensed physician at a crowded medical processing center.

Federal authorities seized Hasan’s computer and searched his apartment in nearby Killeen, Texas, early today, an unidentified U.S. law enforcement official told the Associated Press.

Investigators are examining materials Hasan had with him during the shooting and evidence recovered from his vehicle, which was found parked on the base, a military official told AP.

Facing Deployment

Senator Kay Bailey Hutchison, a Texas Republican, said she was told by Fort Hood authorities the suspect was about to be deployed to Iraq or Afghanistan and had been “very upset and angry” in the past few days.

Initial indications are that Hasan “did not reach out” for help, Army Secretary John McHugh told reporters today.

President Barack Obama yesterday called it a “horrific outburst of violence” directed at soldiers who have dedicated their lives to protecting the nation.

While the deaths of soldiers in battles overseas is tragic, “it is horrifying that they should come under fire at an Army base on American soil,” Obama said in Washington.

The president met this morning with FBI Director Robert Mueller. “We don’t know all the answers yet,” he said at the White House. Flags at the White House and federal buildings will fly at half-staff through Nov. 11, Veterans Day, in a “modest tribute” to the victims, he said.

Obama will attend a memorial service for victims when it’s scheduled, which likely will be before the president leaves on a trip to Asia on Nov. 11, spokesman Robert Gibbs said.

Suspect on Ventilator

Army spokesman Lieutenant Colonel Christopher Garver said the shooting appeared to be the worst in memory at a U.S. Army base. “We think it is,” he said.

The death toll rose to 13 from 12 early today when a woman who was shot died of her injuries, a base spokeswoman said by telephone. All the other injured were in stable condition, officials said at a press conference today, while the suspect is on a ventilator. As of this morning, 27 people are still hospitalized, the Army said.

The shootings began at about 1:30 p.m. local time as soldiers were awaiting dental and medical treatment at the processing center, said Cone. At an auditorium about 164 feet (50 meters) away, 138 soldiers were graduating from college extension courses, and officials were able to close the doors to protect participants, he said.

Lock Down

Military police locked down the base after the shooting, lifting the restrictions hours later after determining the threat was over. The Army is investigating whether the suspect’s guns were registered with the base.

The female officer who shot Hasan is in stable condition at an area hospital, according to the Army.

The Virginia Board of Medicine lists Hasan as a licensed physician with a primary practice at the Darnall Army Medical Center at Fort Hood. It says he received his medical degree from the Uniformed Services University of the Health Sciences in Bethesda, Maryland, in 2003 and completed a residency in psychiatry at the Walter Reed Army Medical Center in Washington in 2007 and a fellowship in disaster and preventive psychiatry in 2009.

While at Walter Reed, where many soldiers wounded in Afghanistan and Iraq are treated, Hasan had “difficulties” that required him to get counseling and additional supervision, AP reported, citing Dr. Thomas Grieger, who was the center’s training director at the time.

Hasan transferred to Fort Hood in July, said Colonel Kimberly Kesling, deputy commander of clinical services at the medical center. She told reporters she helped oversee Hasan and had no indication he was unstable.

‘Hard-Working’

“He was a hard-working, dedicated young man who gave great care to his patients,” she said.

Hasan was a devout Muslim and had sought for several years to be discharged from the military, the Washington Post reported, citing his aunt. Noel Hasan told the paper her nephew endured name-calling and harassment about his faith for years after the Sept. 11, 2001, attacks on New York and the Pentagon.

A military official told AP that Hasan’s family had Palestinian roots.

Cone told NBC’s “Today” show this morning that witnesses reported that Hasan shouted “Allahu Akbar,” or “God is great” before opening fire.

The Council on American-Islamic Relations condemned the shootings and urged calm as investigators piece together what happened.

“No political or religious ideology could ever justify or excuse such wanton and indiscriminate violence,” Nihad Awad, the group’s executive director, said in a statement.

Web Postings

The suspect came to the attention of authorities six months ago because of Internet postings discussing suicide bombings and other threats, AP reported, citing unidentified law enforcement officials.

One of the Web postings equated suicide bombers with a soldier throwing himself on a grenade to save the lives of his comrades, according to the report. Officials are trying to confirm whether Hasan was the author of the postings, the news service said.

Fort Hood, about 60 miles (97 kilometers) north of Austin, the Texas capital, houses about 45,000 U.S. troops and is home to the Army’s 1st Cavalry and 4th Infantry divisions. It is one of the three largest Army bases in the U.S. by population and acreage.

The base has felt the strain of multiple combat deployments, with 10 suicides reported there this year and more than 75 since the U.S.-led invasion of Iraq in 2003, the Washington Post reported.

Cafeteria Killings

Killeen, where Hasan lives, is the site of one of the worst mass killings in U.S. history. A gunman drove his pickup truck through a cafeteria window in 1991 and shot 22 people dead with a handgun before killing himself, AP said.

No other shooting at a military base in the U.S. has been anywhere near as deadly as yesterday’s attack, the news service reported. In 1993, a gunman at Fort Knox shot five civilian co- workers, killing three, and then fatally shot himself, AP said.

To contact the reporters on this story: Margot Habiby in Fort Hood at mhabiby@bloomberg.net; Jeff Bliss in Washington jbliss@bloomberg.net.

Last Updated: November 6, 2009 16:24 EST