Afghan National Army Commandos attend their graduation ceremony in Kabul in July. Foreign combat troops are set to leave Afghanistan by the end of 2014 after handing over all security responsibilities to Afghan forces. S. Sabawoon/EPA/Landov hide caption

itoggle caption S. Sabawoon/EPA/Landov

U.S. troops patrol in the Baraki Barak district of Logar province, Afghanistan. Sean Carberry/NPR hide caption

itoggle caption Sean Carberry/NPR

A soldier from the U.S. Army's 101st Airborne Division on patrol in southern Afghanistan. (October, 2010, file photo.) Chris Hondros/Getty Images hide caption

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From video of the incident, as the helicopter swooped low over a snowy base in Afghanistan moments before crashing in the distance. YouTube.com hide caption

itoggle caption YouTube.com

An elderly Afghan man sits next to the covered body of a person who was allegedly killed by a U.S. service member in Panjwai, Kandahar province south of Kabul, Afghanistan, on Sunday, March 11, 2012. Allauddin Khan/AP hide caption

itoggle caption Allauddin Khan/AP

An Afghan demonstrator holds a copy of a half-burnt Quran, allegedly set on fire by soldiers at Bagram Air Field, during a protest outside the base today. Massoud Hossaini /AFP/Getty Images hide caption

itoggle caption Massoud Hossaini /AFP/Getty Images