I'm really sorry to hear of this. Initially speculation was that it was an ETA attack, but in my humble and uniformed opinion, it sounds a lot like an Al-Qaeda type operation: simultaneous explosions, etc. I can sympathize with how devastating this is. I was in Washington on September 11, and I was scheduled to fly out of Dulles airport that afternoon. It hit very close to home for me.
My best to you, I hope you did not lose any friends or family. From what I can tell right now, my colleagues in Madrid are all accounted for.
fader