A&P anon addendum A&P anon's to earlier analysis. It IS possible for the rotor head to separate on the Sikorsky S76 model of AC; it has happened once before after a blade spar was damaged internally by a lightening strike, resulting in a crash and loss of life. If this happened again it might explain the unusually high speed that the craft was going when it hit the ground.
The maximum safe speed, VNE, Velocity Never Exceed, is 155knots or 178mph and reports show the AC was going 161knots, 185mph upon impact, which would have been totally irresponsible of the pilot under the flight conditions.
https://en.wikipedia.org/wiki/2002_Bristow_Helicopters_Sikorsky_S-76A_crash