That's simple, actually accomplishing the deaths of the President, 4 or 5 Supreme Court Justices, and a couple dozen Senators & Representatives.
Those killed were peons, well, below-peons actually; the normal citizen is a peon, but they [military] were signed up to defend America, and that means that their lives are worth even less. [/governmental-thinking]
Just look at the government's [lack of] response to the Tea Parties --this may or may not be changing, as we had a pretty nice turnover last-election-- as compared to their responses to the Giffords incident. On the one hand you have a non-violent protest-group numbering in the MILLIONS, and on the other a SINGLE political malcontent who dared to strike out at one of the ruling class... and observe that Hasan killed near TWICE as many as the Giffords-guy did and the relative outcry/alarm between the two; it's so supremely messed-up that I submit to you that only something like the above hitting the politically-powerful would result in a death-penalty. {It's worth wondering how/if things for the Guantanamo-bay captives would have gone differently if the 9/11 pentagon-flight had hit one of the Houses (while in-session) instead.}