My only comment at this point - except of course to extend my sympathies to those dead or injured and their families - is that all the moaners about reduced access for spectating should take this on board.
A 180mph 175+kg motorcycle has an enormous amount more kinetic energy (if that is right, but I mean the force that makes it want to continue moving) than, say, a TZ250 of the old days, weighing 130kg and "only" capable of 145mph. If access is restricted, there is probably a good reason for it.