Having a closer look at that tragic pic, is it only everything upstairs of the mast sheared off below the MRH on AS350, or has the whole transmission been ripped off the roof? Perhaps part of a main rotor blade has separated in flight after striking the right wing of piper aircraft, thus causing a massive imbalance and ripping the main transmission and everything attached to it off the AS350's roof. What happened to the piper is clear, the whole right wing has separated from the aircraft.
Anyway, again, not guessing, just wondering.