the advanced warning. if you look at every major terrorist incident against the united states, whether you're talking pan am 103, the world trade center, the "u.s.s. cole" bombing, the bombing in saudi arabia, rarely do you get notice. >> sorry to interrupt you. we have new information from the pentagon. >> reporter: katie, i don't want to alarm anybody right now, apparently it felt just a few moments ago like there was an explosion of some kind here at the pentagon. we're on the e-ring of the pentagon, we have a window that faces out toward the potomac, toward the kennedy center. we haven't been able to see or hear anything after the initial blast. i just stepped out in the hallway. security guards were herding people out of the building and i saw just a moment ago as i looked outside, a number of construction workers who have been working here have taken flight. they are running as far away from the building as they can right now. i hear no sirens going off in the building, i see no smoke. but the building shook for just a couple of seconds, the windows