If you would step back for a second and just think about it, it's pretty goddamn obvious.
A famous person just died in Afghanistan. They were shot by our own troops. Public support for the war is at an all time low - Much has been made of this particular soldier's heroism and character, and how much he believed in fighting for his country. What a fucking PR disaster. Telling people that Al Queda killed him and that he died a hero, charging up a hill and sacrificing himself to protect the rest of his squad is much better press than telling everyone that his convoy was mismanaged, put in a vulnerable position, and someone freaked out and it led to him being shot in the back by our own guys.