To all those Kirkland Theories out there, I'm not here to slaunder you, but what I think speaks against him is that Kirkland and PJ shake hands when Lorelei is already in custody, and ep wise, it is only 1 episode before PJ with the help of Stiles gets her out. Now I know RJ has many helpers, but how what this conversation be? "How are you Lorelei? Oh I shook hands with Patrick the other day"... That seems highly unrealistic to me and imo points towards that Lorelei doesnt know they shook hands, ergo it can't be Kirkland, right? 

Nevertheless I cannot wait for this finale. My guess is Ray or the Sheriff, I cannot put my finger on why, of course there are also things speaking against it, but it's what my gut tells me.