There was a B206 that came apart inflight in st louis, missouri back in 2010. it was a result of low fuel, engine failure, and incorrect control inputs. this caused the helicopter to enter a low/ zero G descent, and Mast bumping/ tailboom contact. the aircraft came apart inflight, and was destroyed. no idea what happened here, but the circumstances seem to fit that same series of events... possible engine failure(for undetermined reason), collective reduced abruptly, and no aft cyclic. aircraft enters zero G dive, and cyclic movements then cause Mast Bumping/ Tailboom contact.