I don't wish to speculate on the cause of this accident, but would like to add to a post someone made earlier on the thread concerning tail rotors. I believe the person who posted was referring to a tail rotor control failure where the helicopter (depending on many factors) could possibly begin to rotate below 40(ish)kts.
The other failure, tail rotor drive failure, as all Puma pilots know, requires an immediate entry into full auto and engines to idle or shutdown before landing. At low level that's not a nice position to be in. I suppose drive failure is a possibility, however, I'd rather wait for the outcome of the investigation than attribute the accident to any speculative cause.