Passing a memorial to those killed, US President Barack Obama and first lady Michelle Obama arrive for a memorial service in Fort Hood, Texas April 9, 2014. Last week, Army Spc. Ivan A. Lopez killed three and injured 16 others at Fort Hood before taking his own life. The shooting was the second deadly rampage at the base, one of the largest US Army posts in the country, in five years. It raised questions about protecting soldiers at home and caring for troops battling mental illness, such as Lopez. [Photo/Agencies]