FORT HOOD - Investigators have interviewed 170 witnesses and victims and still believe suspected shooter Nidal Malik Hasan acted alone in Thursday's deadly shooting spree, Fort Hood officials said.

A motive in the attack is still being determined, said Chris Grey, U.S. Army criminal investigation division spokesman.

With the release of the names of the dead, it was learned that five of the 13 killed were part of a combat stress team. These teams don't wait for patients to walk in a therapist office but instead go out to the battlefield seeking out soldiers with potential psychological issues.