[Franek Grabowski]

Well, I would not call such incident a friendly fire, as they were definetelly unfriendly. I am awared of two commanders treated by their subordinates to be shot down, but one of them was downed by Germans and another stopped flying. There was some immediate joy involved.
I was also told of a certain army commander (name known to me) who was found dead on a battlefield with a shot from the back. A man who was telling me about that, who knew the killed man, noted that what a man [bastard] he must have been if he had not noticed that he is so much hated. A similar story is mentioned by Alastair Maclean in his HMS Ulysses.
Such incidents definetelly happenned, but I would guess pre-war officers or NCOs with a strict and dumb disciplinary approach and no real combat experience were involved. I do not think anybody would kill his commander because of his bad commanding, he must have had been a real pain in the a**e.
Concerning the Kingcome's incident, as far as I know it involved a Winco and occurred with a Canadian Squadron. At least that is what has been told by certain Dilip Sarkar and what was consistent with other data appearing here and there, among others during Piece of Cake controversy.