I just had a thought, several in fact...all the sides and the episode summary for 10x24 point to a terror attack. That coupled with the one picture of a worried looking Arizona (again, completely a subjective reading of the pic and could be a gross misinterpretation of the text) has me thinking, what if a conference or meet of some sort is being held in Seattle to showcase Derek and Callie's work, which is NIH funded, or something they collaborate on and that is where the attack happens? I mean, something like that would have press coverage and politicians, the President himself might come to something like that.
Plus, an oft used terror strategy is to double down by then targeting the hospitals closest to the epicentre of the violence (first wave of attacks) to completely bring down morale and scare people who were seeking help and also those equipped to give it.
Darn, my mind is a dark place.