Pretty sure the boy was possessed by the mammoth spirit (it was an evil mammoth shaman hell-bent on killing humans), and is using the boy to kill off the humans, and stop the glacial hotel…

I really thought the whole show was going down the 'outbreak' lines. An ancient mumps like disease from the mammoth carcase. The boy first, then Ronnie when he touched it. Followed by the 'Fed' girl (notice she coughed after coming out of the cold store?). Like Lost meets twin peaks, with 28days later theme…

Not sure if it was mentioned in the comments already, but the cut hand was from when he stole the boat and beat up the shop assistant. All throughout the last episode he held the gun awkwardly in his left hand and hardly used the right hand. Don't knwo why he hasnt at least dressed the wound though?