I was shocked when I heard about this, at 12:00 the death count was something about 100 and at 14:00 it was already 160! :-(. I hope the Spanish a.org members and their relatives are allright.
Apparently Batasuna says it's most probably a muslim fundamentalist attack and not an ETA bombing. However so short before the elections in Spain I'd bet it's an ETA bombing.
At least one thing's clear, an attack of this scale takes quite a bit of preparation so I think it's safe to say it isn't a single person doing this.
