How did the roof get ripped?

They probably deflate it so it doesnt have a chance to rip or get damaged.

u realy dont no whats going on do you

The roof is held up by air pressure. As the air pressure inside BC place is higher than outside. (hence the need for those revolving doors). When the rip occured the air from inside escaped and the pressure difference was lost. so the roof started sagging in... Thats why in the video the roof is flapping straight up... air was rushing out. Anyway... there are a bunch of mexicans rushing up with some fabric to patch it up (no joke there really is a buch of mexicans rushing up to fix the problem) Thats where the fabric came from...