Four people, including the gunman, died in a shooting rampage at Ft. Hood Army base in Texas on Wednesday. Sixteen people — three of whom remain in critical condition — were also injured. Army officials say the shooting spree lasted 20 minutes before Specialist Ivan Lopez turned his privately owned weapon, a .45 caliber Smith and Wesson, on himself. An Iraq war veteran, Lopez was undergoing diagnosis for Post-Traumatic Stress Disorder at the time of the shooting.