Nov. 5 (Bloomberg) -- Twelve people were killed and 31 were wounded by at least one gunman who opened fire on the grounds of Fort Hood Army Base in Texas, the U.S. military said.

The suspected shooter, a soldier, was killed, Lieutenant General Robert Cone, commander of III Corps at the base, said at a press conference.

“We do not know” what the motive was, Cone said. Witnesses reported seeing “more than one shooter,” he said.

At least one other soldier is in custody. Two others who were apprehended after the initial shooting were cleared, according to Christopher Haug, a public affairs officer at the base who was interviewed on CNN.

The suspected gunman who was killed has been identified as Major Nidal Malik Hasan, said a defense official, who spoke on condition of anonymity.

The Virginia Board of Medicine lists Hasan as a licensed physician who has 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.

Hasan transferred to Fort Hood in July, the Associated Press reported, citing unidentified military officials.

No Further Threat

Military police have secured the base and said there is no further threat, according to an Army statement. The crime is being handled by the Army Criminal Investigation Command and the Federal Bureau of Investigation.

Officials at Fort Hood are “marshalling the medical support and counselors necessary to take care of our soldiers and their families and to notify the next of kin,” Army Secretary John McHugh said in a statement.

McHugh, Defense Secretary Robert Gates and Chairman of the Joint Chiefs of Staff Admiral Michael Mullen expressed sympathies for the wounded and the families of those killed.

“There is little we can say at this point to alleviate the pain or answer the many questions this event raises,” Gates said in a statement. “I can pledge that the Department of Defense will do everything in its power to help the Fort Hood community get through these difficult times.”

Mullen cautioned against speculation before facts are known.

“The Army is investigating,” Mullen said in his statement. “It is important that we let that work complete before we speculate about the circumstances leading to this senseless violence.”

Gathered for Ceremony

The shootings began at about 1:30 p.m. local time at a personnel processing center near the Howzee Theater, where friends and family were gathering for a graduation ceremony for troops taking college extension courses on the base, said Lieutenant Colonel Chris Garver, a Pentagon spokesman.

President Barack Obama called the mass shooting 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, Obama said in Washington, “it is horrifying that they should come under fire at an Army base on American soil.”

Law enforcement authorities and the military will investigate and find “answers to every single question about this horrible incident,” he said.

Obama got a telephone briefing on the incident from Cone.

FBI Investigating

The FBI is on the scene and is working with the Army to determine what took place, Special Agent Erik Vasys, a spokesman for the San Antonio Field Office, whose territory includes Fort Hood, said in an interview.

Nine of the shooting victims were being treated at Scott & White Memorial Hospital in Temple, Texas, according to the hospital’s Web site. All of the patients are adults, the Web site said. More victims are expected and the hospital put out an appeal for blood donations.

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

To contact the reporters on this story: Anthony Capaccio in Washington at acapaccio@bloomberg.net; Viola Gienger in Washington at vgienger@bloomberg.net

Last Updated: November 5, 2009 19:40 EST