I had a fight with two hexen and when I have killed the last one, one of my brothers was still under charm -but still alive. However on a post battle screen, he was listed as dead. And he indeed died game just auto killed him.
I guess it’s a bug as it makes no sense. Either game did not wait for him to de-charm before ending the battle, even as he was still hostile or there is some problem with him still being flagged as hostile before game terminated battle.