Leaving a helicopter idling while a pilot is outside doing what need to be done while one is alone and far away from any civilisation is not a thing from the past but a reality in the Bush and in remote areas. The Aircraft model, AS350 or anything else is not really important as long as everything is done correctly, controls locked etc.
It's not fun when when you are stuck 200 miles from any civilisation and about a 1000 miles from any rescue (flying that is) because you shut it down at a fuel cache and the Darn thing won't start anymore and is in need of a new "igniter box". That's only one reasons, there are others. You use your head.
Now what and why this Pilot did it I don't know but he sure was not alone there. RIP.
Any pilot that leaves his aircraft with the rotors running is eventually going to get his head examined.
That's not a really nice thing to say actually.
JD