I don't think it's the answer either, but I was just throwing shit at the wall to see what sticks. That and drunk. Anyway, to give a better explanation to my own hypothesis, here's a little more.
As far as we're aware, the real time line for this show begins the day that this guy is riding around on the pizza delivery scooter when he saves the boy from getting killed by the heart attack truck driver. However, what if there is another time line that's even in the future of that one and the main character pizza delivery guy has "mastered" his time travel power and can bring his real body back with him and not just take over the mind of a previous version of himself.
So he could have seen the "future him" kill his mother, and he's the same "future him" that is children killer as well. Again, I don't think this is the case at all, but I was drunk when I dreamed up this theory.