NTSB Preliminary Report released.
https://app.ntsb.gov/pdfgenerator/Re...relim&IType=FA
It would appear at some point there was low Main Rotor RPM, the MR Blades cut off the Tail Boom....witnesses saw the aircraft hover, oscillate in the roll axis, then spin right, and pitch down before being lost to sight.
The report removed the possibility of a mid-air collision with another aircraft or drone.