Ok I gonna need to read the previous chapters cos I thought the sister and the big guys were just living next door to the house?
Also what creep him out about the mutants? I assume the mutants eat humans and oh, not the first time he encounter one? Some interesting backstory there!
Zombies (the shamblers) stopped attacking people for an unknown reason (he says so in Issue 1). And Mutants, I assume, are cannibals that eat both zombies and humans.