You wrote, .." I trust in the honour of the Russian officers - they would not assassinate a Marshal of France."
First it was that the Russians couldn't possibly have any reason to assassinate Berthier and now -after the obvious reasons for them wanting to assassinate him have been pointed out- it's that they had too much honor to assassinate a "Marshal of France."
Not sure what sort of bias would motivate such statements. Is it an attempt to ignore the rage and vengeance that burned in the heart of the Russian and German soldiers?
I agree that the out and out killing of Berthier outside of France -while he is still nominally a civilian- would probably not be seen as an honorable act; all the more reason that his exit was via the window.