I stand corrected and now put more credence on the original premise of a maintenance issue. Better pictures have emerged that show blades, rotor hub, shaft, and transmission gyrating through the air as an intact and separate unit. The blades look good, not mangled like they would be if they hit hit the tail empanage. There is some video showing of violent twisting action that probably broke it off. This suggests that something seized violently in the transmission or engine -- transmission more likely because the sprag clutch would have let it free wheel if it had been the engine. That suggests a catastrophic mechanical failure. Could just happen, or could be the eventual outcome of poor maintenance. This will be interesting to follow. I immediately wondered about pilot qualifications. Whether reacting with a bad choice to a fuel emergency or dodging a potential bird strike. But the emerging video shows this to have been sudden and violent. I retract my mast bump theory. Photo you provide also shows cyclic to be removed from left seat position (common in a tourist configuration) so it's not like the kid kicked the controls.