One day, he met a woman who challenged him. She didn't seem scared of him, and even seemed to enjoy playing with him. He began to fall for her, but he knew he couldn't let himself love her.
He knew that if he did, he would be vulnerable to her and she would eventually kill him. So he continued to torment her, flirting with her then rejecting her.
She never understood why he did it, but she loved him all the same. One day, he killed her, and he has never been the same.