US grieves those killed in Texas shooting

America was trying to understand on Saturday just what lay behind Thursday's shooting at a sprawling army base in Texas.

US President Barack Obama said on Friday the entire nation is grieving for those killed at Fort Hood, and he urged people not to jump to conclusions while law enforcement officers investigate.

Obama met on Friday morning with FBI Director Robert Mueller and other federal leaders to get an update on what they've learned.

Thirteen people were killed and 30 others injured in the shooting rampage at the Texas Army post on Thursday.

The suspected shooter is an army psychiatrist; his motive remains unclear.

Obama ordered the flags at the White House and other federal buildings to be at half-staff until Veterans Day.

He called it a "modest" tribute to those who were killed and to those who put their lives on the line in the armed services each day.

He promised that that his administration would update the nation as it learns more about what happened and why, at Fort Hood.

The suspected gunman, Major Nidal Malik Hasan, was shot and remains in hospital.

The shooting spree began as some 300 soldiers lined up to get vaccinations and have their eyes tested at a Soldier Readiness Center, where troops who are about to be deployed or who are returning undergo medical screening.

Nearby, others were lining up in commencement robes for a ceremony to celebrate soldiers and families who had recently earned degrees.

The gunman was struck four times by a civilian police officer who was wounded herself.

Base officials said Kimberly Munley fired on the suspect just three minutes after the gunfire erupted and that her efforts ended the crisis.

Hasan, hooked up to a ventilator, was moved on Friday to a military hospital in San Antonio, Texas, while Munley awaited surgery to remove the bullets from her leg. Her husband was flying in from Fort Bragg, North Carolina.

A moment of silence was held on Friday afternoon at Fort Hood and other US military bases as a mark of respect for the victims.

At a Muslim community center near Hasan's home in Silver spring, Maryland, people described him as a kind, quiet man willing to help. A former imam said he attended prayers regularly, often in Army uniform.

The current Imam, Mohammed Abdullahi, said he couldn't believe the news when a member of his congregation called on Thursday afternoon.

The Imam also said Hasan was a man devoted to his medical studies and never talked about politics.

Neighbors spoke of a friendly generous man. One showed furniture he'd given away after his imminent posting to Iraq.