WASHINGTON -- The Army's chief of staff says the Army is taking a hard look at itself to make certain that something like the Fort Hood rampage doesn't happen again.

The shootings left 13 dead and 29 wounded. The alleged gunman, Maj. Nidal Malik Hasan, was wounded by civilian police.

Gen. George Casey warns against reaching conclusions about motives until investigators have fully explored the attack. Early reports suggest Hasan, a Muslim, was angry about the wars in Afghanistan and Iraq and worried about his pending deployment to Afghanistan.

Casey says focusing on Hasan's Islamic roots could "heighten the backlash" against all Muslims in the military.

Casey appeared Sunday on NBC's "Meet the Press."