breaking any FAR's...well...surprisingly, astoundingly, UNBELIEVABLY!!!...there are *no* regulations that specifically prohibit what he did
Well, I'n not so sure... Were it to have happened in Canada, the following Canadian Aviation Regulation would probably apply:
602.10 (1) No person shall start an engine of an aircraft unless
(a) a pilot's seat is occupied by a person who is competent to control the aircraft;
(b) precautions have been taken to prevent the aircraft from moving; or
(c) in the case of a seaplane, the aircraft is in a location from which any movement of the aircraft will not endanger persons or property.
(2) No person shall leave an engine of an aircraft running unless
(a) a pilot's seat is occupied by a person who is competent to control the aircraft; or
(b) where no persons are on board the aircraft,
(i) precautions have been taken to prevent the aircraft from moving, and
(ii) the aircraft is not left unattended.
In Canada, a helicopter falls within the definition of an "aircraft". I don't know the FAR's as well, but I bet there is similar wording in those regulations too.
I know it goes on all the time, but during my modest helicopter flying career, I have only once left the pilot's seat with anything turning, much less running, and that was under the specfic instruction of the check pilot. I am not at ease with the practice myself - I'd rather wait. (rotor brake makes the wait more preasurable though!)
Pilot DAR