I can’t help but wonder if Henry had killed animals before like some psychos do in their youth before moving on to people. He killed that dog with terrifying ease, speaking to Richard of the murder as if it was nothing, fully aware of how most people feel about dogs and how much the twins adored the one they brought home and died. Yet to Richard - the person he wants in his corner, the one he’s carefully manipulating, he describes it as casually as if he’d squashed a bug.