That's a shocking video, seeing the rotors flying round on their own. Looks like all five rotors are attached to the rotor head so it appears to this
non-expert that the whole assembly came away from the fuselage.
All the countless number of helis I've seen flying in, out & over Aberdeen down the years - the last thing you think about would be the rotor head coming completely away from the aircraft.
Sincere condolences to the families of the Deceased.