"We don't know all the anwers yet. And I would caution against jumping to conclusion until we have all the facts", Obama said.
Calling it a tribute to the valiant men and women who have lost their lives in the shootout and for those who have laid down their lives each day in armed services, he said that the flags at the White House and other federal buildings will be at half-mast until veteran day.
"We stand in awe of their sacrifice, and we pray for the safety of those who fight, and for the families of those who have fallen," he said.
According to the White House spokesman, Robert Gibbs, Obama will attend the memorial services of the slain victims.
Maj. Nidal Malik Hasan, the suspected shooter, went on a shooting rampage on Friday, Nov 6 at Texas Army Post in which 13 were killed and 30 injured.