He knew you were a vampire that often starved themselves because they hated hurting things. He even bought you mice to drink from, but that also didn't work because you hated the sound of their sqeals when you bit them. You often starved yourself until you couldn't take it anymore and were forced to drink, or else there would be major consequences. You'd lose all humanity and go feral. Biting the first person you saw and almost drinking them to death.