With all due respect, unless you've been in a very similar situation, you have no idea whatsoever as to what you'd actually do.
Those poor people weren't just waiting for the fire to reach their floor -- the floor was literally burning their feet and the toxic smoke (jet fuel) was filling their offices. Death was going to happen, but I guess some at least wanted a say in how they went out of this world. They had to know that there were no miracles coming to save them. The fire was ferocious, worse than any I've ever seen, and there was no way to hope for a miracle. It was massive. TV and photos can't begin to capture the immensity and intensity of it. I can't imagine how any firefighters could have gotten past the floors of impact and to those stranded above.
Just how do you know that? God can work miracles anytime there is a righteous purpose for it.