See heres the thing, the school was evacuated at 1:40 from what I hear and we still had school like normal today, so if they were trying to skip class or a test or something they failed miserably. I think it was most likely some dumb shit thinking he was being funny and he's sitting at home scared as hell that he's going to be caught now. The other thing, our football field where we evacuate to is elevated (pictures of it being built can be seen
here) so it really was a disgruntled student they would have been smart and planted the bomb underneath. I'm fairly positive that it could be done without being seen by the cameras and nobody would notice because nobody goes under there. From what I'm told the whole thing was pretty amazingly stupid.
Oh and the school is in Snoqualmie.