Fort Hood, Texas  - As investigators tried to determine the motive behind the shootings at Fort Hood, the largest US military installation in the world, the community continued to struggle Saturday with the aftermath of the deadly rampage.

Blood drives and other efforts to help continued in the adjacent town of Killeen, where spontaneous displays of American flags and crosses for each of the victims had sprung up at local churches. A candlelight vigil Friday night drew mourners onto the base, while a moment of silence was observed at US military installations across the world earlier in the day.

Texas Governor Rick Perry met with many of the wounded victims Saturday in a hospital and told reporters they appeared to be making progress.

"There's some that are going to be a long time healing up, some that will be out in a few days and everything in between," he said.

The US Army named those killed in Thursday's attack, revealing what appeared to be a broad cross-section of the ranks: officers and enlisted troops, soldiers representing multiple ethnic groups and from home states across the country.

Colonel John Rossi called them "brave members of our Army family," before holding a moment silence.

The slain included 12 soldiers and one civilian: Lieutenant Colonel Juanita L Warman, 55, of Havre De Grace, Maryland; Major Libardo Caraveo, 52, of Woodbridge, Virginia; Captain John P Gaffaney, 54, of San Diego, California; Captain Russell Seager, 41, of Racine Wisconsin; Staff Sergeant Justin Decrow, 32, of Plymouth, Indiana; Sergeant Amy Krueger, 29, of Kiel, Wisconsin; Specialist Jason Hunt, 22, of Tillman, Oklahoma; Specialist Frederick Greene, 29, of Mountain City, Tennessee; Private First Class Aaron Nemelka, 19, of West Jordan, Utah; Private First Class Michael Pearson, 22, of Bolingbrook, Illinois; Specialist Kham Xiong, 23, of Saint Paul, Minnesota; Private Francheska Velez, 21, of Chicago; and civilian police officer Michael Cahill of Cameron, Texas.

The alleged gunman in the attack, Army psychiatrist Major Nidal Malik Hasan, 39, remained in critical condition late Friday but was expected to survive. The devout Muslim was transferred to the Brooke Army Medical Centre in San Antonio, Texas, where he remained on a ventilator and was unable to communicate, an Army spokesman said.

At the Scott and White Hospital in nearby Temple, Texas, doctors said just two of the 10 patients brought to the trauma facility remained in the intensive care unit. They were now in stable condition, chief of surgery Roy Smythe said.

The wounded were an "unusually resilient, brave group of individuals," he said, but noted some could suffer from physical or psychological wounds for the rest of their lives.

A total of 30 people were wounded in Thursday's attack and brought to several surrounding hospitals.

In the post-attack soul-searching on the ravages of war and the stress with which soldiers and their families live, authorities have focused on destigmatizing the need for psychological help.

Hasan reportedly shouted, "Allahu Akbar," or "God is great," before emptying two handguns at the Texas base's centre that prepares soldiers for deployment overseas. Rossi said Hasan fired more than 100 rounds.

Gunning down fellow soldiers was both heartbreaking and despicable, US President Barack Obama said during his weekly radio address Saturday.

"It is an act of violence that would have been heartbreaking had it occurred any place in America," he said. "It is a crime that would have horrified us had its victims been Americans of any background.

"But it's all the more heartbreaking and all the more despicable because of the place where it occurred and the patriots who were its victims."

Obama had earlier cautioned against any quick judgements about the shooter's motive: "We don't know all of the answers yet, and I would caution against jumping to conclusions until we have all of the facts."

Obama ordered US flags at all federal government buildings to be flown at half-staff to mourn the victims - 12 soldiers and one civilian police officer.

Details were emerging about Hasan as family and friends expressed shock that he could have committed the crime. But they said that he had grown disgruntled by his pending deployment to Afghanistan.

Colonel Catherine Abbott, an Army spokeswoman, confirmed Friday that Hasan was being deployed to Afghanistan but could not provide a timeframe for his departure. He was to join a reserve unit for treating combat stress.

US media reported that Hasan had sought to be discharged from the Army, and relatives said he was horrified about the possibility of going to Iraq or Afghanistan and had grown tired of being harassed by other soldiers because of his faith. Hasan reportedly opposed the wars in Iraq and Afghanistan and was not shy about conveying his position to co-workers and friends.

As an Army psychiatrist, Hasan had treated soldiers returning from both conflicts for post-traumatic stress disorder and other ailments. He was facing his first deployment to a war zone since he joined the Army in 1995.

Born in Virginia, Hasan grew up in the Washington area and frequented the Muslim Community Centre in Silver Spring, Maryland, which borders the nation's capital.

"I've known him since 2007," the centre's imam, Mohammed Abdullahi, told the German Press Agency dpa. "He was quiet, normal. There was nothing crazy about him like everyone is making it out to be. He didn't look crazy."

The shootings shocked a military base accustomed to grieving for soldiers killed in combat. The rampage brought the wars closer to home and highlighted the growing stress on the men and women who have been repeatedly deployed to Iraq and Afghanistan for extended combat duty during the last six to nine years.

The mental health of soldiers has become an increasingly high priority for the US Army, which has been coping with a high number of suicides by soldiers who returned from battle. (dpa)