US First Lady Michelle Obama and President Obama walk past the Fallen Hero Memorial at Fort Hood on November 10, 2009 during a service honoring the soldiers and civilians killed in a shooting rampage on November 5. US Army Major Nidal Malik Hasan, 39, a psychiatrist and specialist in combat stress, who allegedly killed 13 people and wounded 42 in a shooting rampage at Fort Hood, is believed to have acted alone by investigators and no motive has been established. Getty Images logo Getty Images 27 months ago

US First Lady Michelle Obama and President Obama walk past the Fallen Hero Memorial at Fort Hood on November 10, 2009 during a service honoring the soldiers and civilians killed in a shooting rampage on November 5. US Army Major Nidal Malik Hasan, 39, a psychiatrist and specialist in combat stress, who allegedly killed 13 people and wounded 42 in a shooting rampage at Fort Hood, is believed to have acted alone by investigators and no motive has been established.