Originally Posted by MSD

WTC 7 suffered damage from fire and impact of debris from the towers, a section 10 floors high was scooped out to a depth of 1/4 to 1/3 of the building's area.

First of all, the fire burned for 9 hours. The sprinkler systems required manual activation of pumps and everyone had already evacuated. NIST reports indicate that a pressurized diesel fuel line running to the 5th floor generators was not a major cause as previously theorized, but that fire was fueled constantly until fuel tanks were empty. Two hours before the collapse, the building was visibly buckling because the fire had weakened its structure.

WTC 7 was constructed with a combination of support beams and transfer girders. Upon structural failure of any support, the load would be transfered to surrounding beams. Column 72 on the 13th floor was the first to fail due to decreased strength from fires. Loads were transferred toward the east end of the building, and the east penthouse collapsed, overloading support structures and allowing collapse to progress toward the west of the building.

WTC7 did not collapse at freefall speeds. Go back to the video, and look at the top left of the building as the video starts. What you see at 2-3 seconds is the East Penthouse collapsing. For the next 7 seconds, columns are failing until they can no longer support the building and it collapses in on the most heavily damaged part, with intact sections holding up the longest.

"We decided to pull it" is another truther favorite, claiming that it means they were going to demolish the building. Unfortunately for them, this is not a phrase used by demolition contractors. On the other hand, if "it" refers to emergency services' attempts to save a building that was already a complete write-off due to extensive structural damage and several floors engulfed in flames in addition to a fire on the 5th floor fed by a pressurized diesel line (used to supply generators) with tens of thousands of gallons of fuel oil in the basement and no way to safely shut it off, it makes a lot more sense.