At first when I reached the rooftop I could not understand what was going on. I could see the North Tower clearly, but the South Tower was completely covered in a cloud of smoke. It took me a few minutes to realize that the tower wasn't there anymore. The cloud of dust was so high that it could have had completely consumed the whole height of the tower.

Only two or three minutes later could I see patches of blue sky in a spot where the South Tower was supposed to stand. I couldn't believe my eyes. I could have never imagined that a building of such magnitude could collapse from a fire damage that only 30 minutes ago seemed to be localized to a small part of the building.