Riser

Riser is a quite mysterious guy. He is completely silent, talking only if 100% necessary, and expresses no emotion. Even those close to him never hear him speak, and know no more about him than a random stranger. If you somehow get him to talk, all that you'll discover is that he has no emotions at all. He seems to have the personality of a common zombie, all instincts and no empathy. Is it possible that he'll go rogue, and attack his own family?