Thus there are three kinds of injury in transactions; those done in ignorance are mistakes when the person acted on, the act, the instrument, or the end is other than the agent supposed; the agent thought either that he was not hitting any one or that he was not hitting with this missile or not hitting this person or to this end, but a result followed other than that which he thought likely (e.g. he threw not with intent to wound but only to prick), or the person hit or the missile was other than he supposed.