On 9/11, WTC1 Hit WTC7, Seriously Damaging the South Side
"The biggest decision we had to make on the first day was to clear the area and create a collapse zone around the severely damaged 7 World Trade Center, a 47-story building heavily involved in fire. A number of fire officers and companies assessed the damage to the building. The appraisals indicated that the building's integrity was in serious doubt.
I issued the orders to pull back the firefighters and define the collapse zone. It was a critical decision; we could not lose any more firefighters. It took a lot of time to pull everyone out, given the emotionalism of the day, communications difficulties, and the collapse terrain. - FDNY Chief of Department Daniel Nigro, Report from the Chief of Department, Fire Engineering, 9/2002