It was mildly surprising to me that the comment to the original post in this thread seemed to focus on the existence or non-existence of God, rather than the kind of comment (He deserved it! Fuck'im! etc.) that I was expecting.
The saddest and most depressing thing about the comments was the complete lack of moral outrage, predictable though it was.
My basic feeling here is that with God or without, this act will be avenged in the long run. In a universe totally devoid of God, there is still some kind of moral force or karma operating, such that, in an action as heinous as this, the actors have sown the seeds of their own destruction.
I think of it as waves of revulsion spreading across the globe, interacting with earlier and later waves and generating some kind of deadly hatred that may have to simmer for a long, long time. At the same time, among the murderers themselves, I see the "successes" of the operation creating waves of triumph, stoking the aggression, cruelty and hatred (or maybe it's just cold indifference) that enables these men or women to kill people on the other side of the world by the touch of a button. The violence feeds upon its own "success" and ever more savage attacks are launched against the world from the underground bunkers of Nevada.
Every action has its consequences. It is the build-up of these consequences that I think will finally lead to the downfall of the USA.