PETER BERGEN, CNN NATIONAL SECURITY ANALYST: I’m reminded of Oklahoma City, which was a bombing, but first treated as a gas explosion. First reports are often erroneous. The fact there were two explosions, two bombings — One of the things I would be looking at is, once the devices, if it is a device, is found, what kind of explosives were used? For instance, if it was hydrogen peroxide, this is a hallmark of Al Qaeda. If it was more conventional explosives, which are much harder to get a hold of now, that might be some other kind of right-wing extremists. We’ve seen a number of failed bombing attempts by Al Qaeda using bombs … We’ve also seen other extremist groups attacking, right-wing groups, for instance trying to attack the Martin Luther King parade in Oregon in 2010.