I think the killer and the issac is different, although by appearance it may seem that issac himself is the killer, but by analysing his chin and hair it is clear that issac is not the killer, maybe issac only killed his brother due to some unsettled feelings or whatsoever but he is not responsible for any other deaths, in the last chapter giselle did shoot her but i think that she purposely did that to save him, she didn't shoot any vital spots and somehow issac survived and because of blood loss and by not drinking human blood for long time he is now in this state like as a child and the killer is following them as he know that they look similar or they think that issac is the killer..
Well it's just a theory of mine, maybe I'm wrong but let's see in the next season..
Well it's just a theory of mine, maybe I'm wrong but let's see in the next season..
