Responses
from the early chapters that he unconsciously holding something sharp on Gunwoo's neck, also the nightmare he get every night, i think i can agree with you..
or maybe mc was just defending himself from the friends & family that became zombies?
Theory: What if MC was the one who caused the apocalypse? What if he has an alter ego? A different personality, and all the past bad things or mistake he did were forgotten becuz of a trauma — and this amnesia made him for the better