A reminder that Pokemon trainers are not in control of their Pokemon. Pokemon can and have left their pokeballs on their own, and can and have been hurt by their own pokemon, and there are most likely a ton of scenarios where a Pokemon trainer was murdered by their Pokemon.
Pokemon only stay with trainers who they feel offer them something, whether its power, companionship, free food, etc.
Any pokemon trainer (human) who thinks they're in control can and will learn a deadly lesson.