Uh, you are saying that PTSD had nothing to do with him murdering his family?   Murder suicide is quite rare, thats true, but if the guy had, say, a well known genetic deficiency which contributes to violence then that would certainly go a long way to explaining that violence.   Thats sort of like arguing that smoking can't cause cancer because not everybody who smokes gets cancer.   Whether it perpetuates the stigma or not, it seems pretty clear that PTSD contributed to this atrocity.  Otherwise, we might as well say we don't need to focus on PTSD because violence never happens to others.   

   For the past three years we've seen family violence increasing amongst those in the military who have served overseas.  I think we can most definitely link PTSD to not only murder but violence.  That murder is more anamolous is sort of beside the point.