Heroine whose shots ended the slaughter

Schools were closed, streets deserted, and checkpoints set up at entrances to Fort Hood last night, as investigators tried to establish how a lone gunman was able to plan and carry out one of the most deadly killing sprees in US military history.

The death toll from Thursday's attack rose to 13, with another 30 injured during the incident that saw the suspected attacker, Major Nidal Malik Hasan, open fire on a group of 300 unarmed soldiers waiting for check-ups at one of the base's medical facilities.

Victims are still undergoing surgery, and doctors warn that the number of fatalities may still rise. Lieutenant-General Bob Cone, the base commander, said the death toll could have been far higher had it not been for Sergeant Kimberly Munley, a civilian police officer who arrived at the scene roughly three minutes in, and managed to disarm Major Hasan after shooting him four times.

Sgt Munley was wounded by a bullet that passed through both her legs. Her actions were "amazing and aggressive," he said. "She was... one of our most impressive young policemen. She walked up and basically engaged him. I think, certainly, this could've been far worse."

Eyewitness reports suggest the attack unfolded shortly after 1.30pm, as the troops lined up for eye tests and inoculations at a group of buildings known as the Soldiers Readiness Processing Centre. The gunman was armed with two pistols, one of them automatic.

Chaotic scenes were described by Lt-General Cone, who spoke with several victims. One told him: "I made the mistake of moving and I was shot again." Others recalled how they managed to "scramble to the ground and help each other out".

Officials are not ruling out the possibility that some casualties were victims of "friendly fire" from police officers. Lt-General Cone admitted it was "counterintuitive" that a single shooter could hit so many people, though the massacre occurred in "close quarters" and involved "ricochet fire".

About 50 metres away, 138 soldiers and their families had been about to begin a graduation ceremony. The doors to their auditorium were blockaded, and a siren prompted them to evacuate the building, preventing what could have been a far worse tragedy.

Since Major Hasan's religious convictions were seemingly a factor, the attack represents a fresh public relations challenge for America's Muslim community. At the White House yesterday, President Obama warned against "jumping to conclusions" about the massacre until "all the facts are known". The Muslim Public Affairs Council meanwhile condemned the "heinous attack" on behalf of the entire community.

There is no evidence of a terrorist conspiracy, and three other soldiers who were questioned were soon released.

Security has now been stepped up at all US military facilities. Officially, the only soldiers permitted to carry firearms at Fort Hood are members of the Military Police. However, vehicles entering and leaving are not usually checked. Major Hasan was seemingly able to drive into the 350 square-mile base with both weapons, plus a large quantity of ammunition, in the boot of his car.

His two pistols, one of them semi-automatic, were not army issue. But the military psychiatrist is unlikely to have experienced difficulty obtaining them: Texas has some of the most relaxed gun laws in the developed world.

In the absence of a serious challenge to the right to bear arms, public attention may now shift to the enormous pressure now being placed on serving US forces. Major Hasan is the fourth serving soldier to open fire on fellow troops since the start of the Iraq war in 2003.

Fort Hood, near the town of Killeen in central Texas, is America's largest military facility, holding roughly 70,000 serving troops. Half of the eight brigades stationed there are currently in Iraq or Afghanistan, and 685 men based there have been killed since 9/11.

Many of the troops have carried out three tours, and psychological problems are said to be widespread. Now an already stressed community, used to terrible losses overseas, must face a devastating blow on its doorstep.