I find it bizarre that a ground run, with no intent to fly falls through the regulatory cracks and apparent commonsense practices.
Agreed, when the rotors are turning, you are flying - just because you haven't lifted to the hover doesn't mean you can sit there with your head up your a*se.
In the military, we have always had a clear difference between a ground run for engine testing/leak checks etc and rotors engaged ground runs (REGR).
A REGR would be briefed and authorised like any other flight with due consideration for what might go wrong including the need to lift to the hover so the pilot was always ready.
As 212man says, the pilot's behaviour in this incident was so clearly outside the bounds of basic professional discipline and airmanship and a complete abdication of his duty of care.
Does anyone know if the relatives of the deceased and injured to legal action against the pilot?