Sometimes a sensation come to me of how much of an insane situatiin it had to be for the people in that first building, especially the ones that somehow miraculously survived near the impact site. Just a normal work day and suddenly complete pandamonium. No clue what's going on, fire and smoke everywhere and everythibg inside is unrecognizable. Then you hear another gigantic explosion from the second plane hitting and then suddenly eveything violently shakes and it's lights out. A complete nightmare that seemingly came and go in a flash.
The ones that called in sick or slept in must've felt surreal.