Former top Pentagon officials investigating the attack at a Texas Army post have visited the site of the shootings and a military hospital.
Clark says hearing stories about first responders was "very, very encouraging."
The investigators will examine procedures for identifying volatile U.S. military service members hidden in the ranks and lapses that might allow others to slip through unnoticed.
West said since it is not a criminal investigation, it's doubtful they will try to talk to Maj. Nidal Hasan, who's been charged in the killings. He remains in intensive care at a military hospital.