Tower 1, a jetliner crashed into it, tower 2, a jetliner flew into it, tower 3 (WTC 7) just fell???

Why did WTC 7 collapse?

What did he mean we made the decision to pull WTC 7? Pull it down? As in demolish it? Why would they? How could they find time to strategically place explosives to ‘pull’ it down. The explosives would have had to be already in place.

WTC 7: Pull it?