Reply #21: There are basically three possibilities

[WeDidIt]

1) International Islamist terrorist.

2) Domestic Right Wing terrorist.

3) Domestic Islamist terrorist.

Of the three, I would say it is more likely to be domestic in nature. International Terrorists have historically gone for the "big event" as opposed to something smaller. Domestic Terrorists have historically used smaller devices, McVeigh being the exception. You hear about right wing terrorists being arrested with pipe bombs and other explosives. Eric Robert Rudolph is more of an example of the typical right wing bomber. He used smaller explosives and targeted abortion clinics, gay bars, and the Olympics. Had this device actually exploded, from the description, it would have been localized and would not have caused any dramatic structural damage, like McVeigh's device did.

I'll admit that the third possibility could be what happened here, too and given the nature of these types of attacks, I would not rule out attack from somebody like Major Nidal Hasan.