61.   The south tower had fallen.

62.   The south tower was collapsing.

63.   Then came the collapse of the south tower, making clear that the neighborhood was unsafe.

64.   Then the south tower seemed to stoop, swinging gradually toward the Hudson River, ferociously testing the steel skeleton before snapping back.

65.   They were on the phone when the second plane struck the south tower.

66.   They were standing in the lobby of the south tower, which was decimated only a moment later.

67.   Those in the south tower were still spectators, if wary ones.

68.   This very stairwell was the sole route out of the building, running from the top to the bottom of the south tower.

69.   Torch-cutters are slicing through some of the last structural steel remaining on what had been the southern face of the south tower.

70.   Twelve minutes later, it made another sharp left, to settle on a course leading directly to the south tower.