I think the killer is that one guy who was in the military. cause when sookie says something like i wish bill was here, that guy goes i wish some dead ppl were here too. and he could mean ppl in the war but i think its kinda hinting at the fact it was him. and if you notice he is so messed up like mentally about alot of stuff. i just really think it was him.
but idk im not really good at like detective crap but i just get a feeling its that guy.. lol.