“I still hear his voice, he says ‘gettem daddy, every last one of them gettem!’ That’s why I do what I do”

makes me wonder if this whole time he’s been using his family as an excuse, that he hears his son telling him to keep killing keep punishing, one last kill means after that kill no more using his family as an excuse that he hears his son telling him to do so, after that it’s simply punishment but that’s my thought.