One tell in mystery/serial killer thrillers is the nicest one will be the killer. Ebert has a term Law of Unecessary Characters. Dude doesn't quite fit that, he's there to humanize Reis a little. But, he's a local. Trusted member of the cimmunity. He's out in the wilderness fishing/hunting or whatever, and in town with a business.
One easy example is David Fincher's adaptation of The Girl With Dragon Tattoo
remember barely trying to figure out the killer, and it was obvious it was the most charming most reasonable character that was introduced, which would apply to the Viking dude here.
Not that invested in this to figure much out, but it would also kind of fit with the shows ethos of it being the nice guy. Other characters are obviously corrupt, but probably not truly the evil villain. The fat commissioner dude and John Hawkes.