None of them. They just turn and stare, not a single person hits the deck, and the cop has no fucking clue either. If a blade snapped off and clearcut the whole pack of oblivious gawkers, shrugging with a tilt of the head would be the order of the day.
Also, the only airshows worth going to are the big model airplane conventions, if just because you can buy some of the aircraft without being a multi-billionaire or a soveriegn nation. Also if just because a crash is unlikely to kill several dozen people in a blink.
Yeah, speaking from long career as an Apache Pilot playing Jane's Longbow, I'm guessing it was some sort of attempt at an auto-rotational landing following an engine problem, though the engine seems to have still been going? Maybe the guy is just an idiot.
When helicopter blades are flailing wildly out of control, I am the cop asking the crowd to stand back, not this chick who apparently thought this was part of the show.