Initial Moments of the Collapse of WTC1

You can watch the first few seconds in slow motion here. Load this movie:
911.wtc.1.top.slow.wmv

This movie shows the same scene from a slightly different angle (northwest):
http://www.terrorize.dk/911/wtc1dem6/911.wtc.1.demolition.northwest.mpg

About a week ago, I posted a long article by Wayne Trumpman who analyzed the initial collapse of WTC1. I'm really not clear how he could measure the collapse of the first few floors, when the whole thing seems very different to me.

What I see is, right before the rapid global collapse of WTC1 begins, is a slower phase where the very top of the tower starts sinking down several floors. This is not clearly accompanied by large puffs of smoke until the very end.

What is most odd about this is the way the top ten or so floors of the building simply shrink down without any obvious crumpling of the outer facade. There is hardly even any significant bowing of the outer walls to account for the approximately fifty feet of height lost! It is the damndest thing. I can't quite figure what this means, in terms of how the demolition was done. It certainly is not what you would expect for a fire-induced collapse. It is more like the early stages of the demolition, much like the penthouse of WTC7 starts sinking a few seconds before the whole building goes down.