I went Njerpez hunting with my dog leashed.
Found one and chased him shooting till he went unconscious.
Closed in to deal the final blow. My dog went over him attacking.
I attacked the tile where both were and the "final blow" menu displayed (only displayed for unconscious targets) and I thought it was targeting the njerpez. I selected point neck with my hunting knife and it ended up targeting the neck of the dog which was conscious.
Supposing it could be that I was targeting the njerpez and I just failed and hit the dog but it's suspicious that I hit the same targeted body part. In any case, if this is not a bug, there should be a target menu selection, even if there's a chance for you to fail and hit the other creature.