Couse walrider kills every one!
I think he killed him because Chis was going to kill Miles because, as we know even though Chris is insane madman he is aware of the walrider existence and plans to kill all possible host of the walrider. And of course I'm sure the walrider doesn't like that since he needs a host.
Because Chris is trying to Contain the Walrider and the Walrider is trying to find a new host.
He prabobly needs a host not buffed up that looks like Frankinstien remake.
The walrider needs a host and Mr. walker is killing every host he can find, meaning when the walrider runs into chris thanks to him throwing you the other way, the walrider turns chris into spaghetti by pulling him into an air grate stopping him from killing his next host who has seen horror in spades, aka you. plus the walrider can't use chris because he undergone a different experiment which turned him into a giant muscular pin cushion and most likely made him immune to the walrider's ability to possess a host so basically chris walker is a threat to you but to the walrider he is just a pest who is making things so much worse. also walkers death is kind of sad since even though he rips the head off your body when he finds you he is just trying to help stop and contain the walrider and save a nearby town...the collecting of heads is the insanity talking.
Frankenstein is the Doctor who made the monster...plus he's not that buff he's like a twig
What do you think?