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So they instantly lost the main rotor? Same thing happens in mast bumping.

Here's the best explanation I know of: https://youtu.be/jDg1G2y8ZX4?t=293

(As far as I can tell no-one has made an animation of what happens.)

If they survived the crash, it probably was something necessitated an auto rotation, rather than the main rotor departing the helicopter. If that happened they would almost certainly be dead. If the nut on the top of the rotor mast detached - called the Jesus nut - they would also be dead. Mast bumping probably wasn't the cause either since that is a problem mostly constrained to a type of rotor system that wouldn't typically be used in an air ambulance setting. I'm not sure if I know of any helicopters with an underslung rotor system that are used by EMS operators.

> If they survived the crash, it probably was something necessitated an auto rotation, rather than the main rotor departing the helicopter

Good point, went down like a stone is unlikely to be true.

> a type of rotor system that wouldn't typically be used in an air ambulance setting

Sure, I didn't phrase my comment very well, hadn't meant to imply otherwise.

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