I am in no way implying this is what happened, and I am content to wait the year or however long it takes for the AAIB to do their usual thorough job, but heres a scenario for the seasoned 135 chaps to comment on. How do you get yourself out of this one?
We are transitting back to base, I say we, you are the handling pilot and I'm sat next to you. I develop a very sudden and massive panic attack, (never had one before, no idea why it's happening, could be stress, but there you go, it's happening). All I know is, I want this flight to end now and I want to be back on the ground right now.
In my blind panic to get back on the ground, I reach over and flick the engine switches to off. Immediately followed by pulling the rotor brake on. My actions are irrational, but thats a panic attack for you.
As soon as you try to correct either the eng switches or the R/B, I push down on the collective to speed up my return to the percieved safety of the ground.
How long would it take for us to reach the ground from 700(ish)'?
Supposing you manage select one engine switch back to flight, (before I turned it off again), would the relight on a hot engine go with a 'pop', similar to a 'misfiring' engine?
Once again, not saying this is what happened.