A good idea would be to vote for the scummy person.
Zak didn't claim vig but he admitted the softclaim was a blatant lie, which I don't see any good reason why he would want to lie.
PX, you may have a list but you don't announce you're going to shoot someone at night if you're not a vig. Zak specifically said he was going to shoot someone, which heavily implied he had such a role.