Aww, he had to kill the fox, his only neighbour! Or maybe he didn't have to? Perhaps he was just to depressed himself to see any hope for mumfox?
"All fight and fire gone." It's slowly draining out of him, isn't it? The fight against the beast and the fight for Marie. The taking-care might be the only thing to link him to humanity now, and it might be good that Marie is not there to be the object of this need. Not good for him, of course, but good for any chance the two might have at a partnership between equals.