In no way is Brett Partridge Red John. I really cannot see how he can make others follow him. I know that RJ can play the role of anyone he wants to but Plotnick just does not have the attributes of an RJ in real life - how can he all of for sudden be irresistible if the real life actor is not. He might be a good actor but I think he was part of tyger, tyger. When Patrick met him in season 6 episode 1 he seemed very nervous. I think RJ killed him because Brett couldn't keep it together anymore. He posed a threat to the wider organisation and that's the reason he was killed.