locations, obviously there are thousands of other locations that remain vulnerable and become even more vulnerable. so this is kind of i would say a competition between us and the terrorists that goes on and on with tragic result, as we have seen today. >> fran townsend, the fbi are obviously raking over any possible clue. two areas i would imagine are extremely useful. closed circuit video, which there was a lot in this area, and also cell phones, because all cell phones were locked down pretty quickly, presumably to try to stop them using them to trigger the devices, he or she. we don't know who it is, obviously. in terms of going forward, are those two areas going to be key? >> those two and i would add one more, piers. i would also add any of the forensic data that can be gleaned from the bomb site. so the container that may have contained the bomb. if they've got unexploded,