How does Heathcliff seem to be nonhuman in this scene (Chapter 15)?

Heathcliffe laments that he has meen emotionally murdered. Their reunion was bitter-sweet: though passionately glad to be reunited, Catherine accused Heathcliff of having killed her, and Heathcliff warned her not to say such things when he would be tortured by them after her death––besides, she had been at fault by abandoning him. She asked him to forgive her, since she would not be at peace after death, and he answered: "It is hard to forgive, and to look at those eyes, and feel those wasted hands... I love my murderer––but yours! How can I?" (163)