1.   He was two blocks away when the towers fell, and he saw everything.

2.   And where, exactly, in the skyline were the towers they watched fall from places like Lovelock, Nev., and Pope, Miss.?

3.   At another point, bin Laden expressed surprise that both World Trade Center towers fell to the ground, saying he expected only the top floors to collapse.

4.   A signal tower fell across the second-to-last car and had to be removed with a crane.

5.   After the second tower fell, the entire area was consumed with smoke, as if clouds had descended and enveloped the lower tip of Manhattan.

6.   After the towers fell, he searched for his son, but located only his fire truck, smothered in debris.

7.   After the towers fell, officials confronted obstacles that went beyond just the collapse of the command center.

8.   After the towers fell, she tried calling Hall, but the circuits were constantly busy.

9.   But it pulled sharply upward and away just as the tower fell.

10.   But others surmised, based on an understanding of how the towers fell, that more remains could be found below ground level.