I am sure this story is being covered in the USA, but I found a NYT article useful.
a mentor to other veterans, sometimes taking them shooting at a gun range near his Texas home as a kind of therapy to salve battlefield scars, friends said. One such veteran was Eddie Ray Routh, a 25-year-old Marine who had served tours in Iraq and Haiti.

But on Saturday, far from a war zone, Mr. Routh turned on Mr. Kyle, 38, and a second man, Chad Littlefield, 35, shortly after they arrived at an exclusive shooting range...
Link:http://www.nytimes.com/2013/02/04/us...it_th_20130204