Gen. George Casey says focusing on the Islamic roots of Maj. Nidal Malik Hasan (nih-DAHL' mah-LEEK' hah-SAHN') could "heighten the backlash" against all Muslims in the military.
Casey says diversity in the military "gives us strength."
Casey declined to answer questions on ABC's "This Week" about the investigation into the shooting, but said evidence to this point shows that Hasan acted alone.