Like I said in another post... al Queda loves to return to the site of previous hits. Look at yesterday -- hitting Bali again. They tried to attack one of our ships a couple of weeks ago in the gulf and they never received proper 'credit' for their first hit in Oklahoma.
Not receiving proper credit seems to annoy them intensely. They now generally issue statements after the fact, but the Murrah hit would probably have been early on in their US career.
Ain't that the truth...