US President Barack Obama has said the "entire nation" is grieving after a shooting that killed 13 people at a Texas army base.

美国总统奥巴马称，德克萨斯军事基地枪击案之后，“整个国家”陷入悲痛之中。

He said he had ordered all flags at the White House and other Federal buildings to be flown at half mast（下半旗） until Veterans Day on 11 November.

Meanwhile hundreds of people held a candle-lit vigil（值夜，监视） at the Fort Hood¹ base.

Major Nidal Malik Hasan, 39, a US-born Muslim and army psychiatrist²（精神病医师）, opened fire at Fort Hood on Thursday.

He was due to be deployed³ soon to Afghanistan, a military official said.

Family members said Mr Hasan was strongly opposed to the deployment⁴ and had wanted to leave the army.

Mr Obama cautioned against "jumping to conclusions（遂下断语）" and said the motives⁵ for the shooting were being investigated.

"What we do know is that their families, friends and an entire nation are grieving right now for the valiant⁶（勇敢的） men and women who came under attack yesterday," he said on Friday.

He added that the order for flags on federal buildings to fly at half mast was a "modest tribute to those who lost their lives".

Later Japanese media reported that Mr Obama had asked to postpone⁷ his visit to Japan next Thursday by a day so that he could attend a memorial service for those killed.

The chief of staff of the US Army - Gen George Casey - said the attack had been a "kick in the gut⁸" for the entire army.

On Friday, US soldiers and civilian⁹ residents at Fort Hood attended a candle-lit vigil in honour of the victims of the shootings, many crying and bowing their heads.

"Remember to keep breathing ... keep going," Chaplain Douglas Carver told the crowd, quoted by AP news agency.

Over 100 rounds fired

The attack began at about 1330 (1930 GMT) on Thursday at a personnel and medical centre at Fort Hood - the largest US military base in the world, home to about 40,000 troops.

The commander of the base, Lt Gen Robert Cone¹⁰, told NBC News that, according to eyewitnesses¹¹, Mr Hasan had shouted the Arabic phrase "Allahu Akbar!" [God is great] before opening fire.

Deputy commander at Fort Hood, Col John Rossi, later said that more than 100 rounds were fired during the attack.

Col Rossi also confirmed earlier reports that the two handguns carried by Maj Hasan were not military arms, but "privately¹² owned weapons".

He said that the suspect - who had been on a ventilator（通风机，换气扇） in a civilian hospital - was transferred on Friday by helicopter to the Brooke Army Medical Center in San Antonio, Texas.