Its absurbed to even suggest pre-set timers in the context of this if it was a demolition, as you demonstratably have little imagination and can only see this in black and white I'm done debating the point.
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So you are saying they were watching the building and detonated explosives as the tower tipped. Some how timing the ensuing explosions lower down the build. You are suggesting one or the other. I have loads of imagination thanks.