AP Photo

t is impossible to make sense out of the tragic killing of 16 Afghans by a presumably deranged American soldier on March 11. Our hearts go out to Afghan friends; our national sorrow and condolences and apologies are profound and heartfelt.

I cannot rationalize this tragedy. On such a sad occasion, I can only reiterate what Afghan, American, and other NATO and International Security and Assistance (ISAF) troops do together on a daily basis in Afghanistan, to provide some broader context and perspective.