TWELVE people were killed and 31 injured in a shooting yesterday at the Fort Hood military base in Texas.
One gunman was killed in the incident and a suspect was in custody early today. Two other suspects were released. All were American soldiers.
Lt Gen Bob Cone said the motive for the shooting was not known. One of the dead was a policeman, others were soldiers.
President Barack Obama described it as “a horrific outburst of violence".
The army has named the gunman as Major Malik Nadal Hasan. He was reportedly due to be sent on a mission to Iraq.
The dead suspect was believed to be in his late 30s. A law enforcement official said that investigators were trying to establish if Hasan was his birth name, or if he had changed his name after converting to the Islamic faith. In the aftermath of the incident, other US bases across the country stepped up security as a precaution.
Speaking at a press conference in Washington, President Obama said: “It is difficult enough when we lose these brave men and women abroad, but it is horrifying that they should come under fire at an army base on US soil."
He extended his condolences to the families of the victims, adding: “We will make sure that we get answers to every single question about this horrible incident." Mr Obama said the White House was working with the Pentagon, FBI and Department of Homeland Security to make sure Fort Hood was secure.
Fort Hood, near the town of Killeen, is the largest US base in the world.
Home to about 40,000 US troops, the base lies between Austin and Waco, about 60 miles from each city.
Lt Gen Cone said the shooting had begun at about 13.30 (19.30GMT) at a personnel and medical centre at Fort Hood, where soldiers who are preparing to deploy go for last-minute medical check-ups.
He said the shooter, who had two handguns, had opened fire and “due to the quick response of the police forces, was killed".
Two more suspects were apprehended in an adjacent facility, he said, adding that some eyewitness accounts suggested there might have been more than one shooter.
A serviceman stationed at Fort Hood who asked to remain anonymous said: “I heard the emergency announcement over the speakers outside and saw people rushing to get indoors.
“In our office we're okay but we're hearing about the deaths. It's horrible and very shocking.”
Units at Fort Hood are among those deployed in Iraq and Afghanistan, and some will have returned from there.
Hilary Shine, of the Killeen Fire Department, said Fort Hood was like a small city.
“It has schools, a hospital, a convenience store even. And it has a large daytime population – including civilians working on the base – with as many as 80,000 in this area during the daytime."
Texas Senator Kay Bailey Hutchison said in a statement: “I am shocked and saddened by today's outburst of violence at Fort Hood.
“My heart goes out to their loved ones."