SpoilerWell Shane did what he had to do, he was crippled and Otis can't out run the zombies so either all 3 people die or 1 person gets sacrificed, i don't really see any way out of that situation and the entire thing was Otis's fault in the first place accident or not
Spoiler
I totally disagree... Shane seems to have a pattern of homicidal behavior. He almost gunned down his best friend in the woods because he wanted some more winky-time with his wife. When Shane collapsed the first time and told Otis to leave him, Otis did the right thing and pushed him to keep going... Well if Otis would've had any idea what kind of man he was rescuing he might've decided to just leave him, but he didn't and it cost him his life. He might've been trying to make it right, but he didn't need Shane's help in the form of a bullet in the kneecap. How could you support a character who kills his own? They could've made it together perhaps... Now we'll never know.