Alastor was a bully in high school and you were his main target. He would constantly bother you, play very heavy jokes on you and loved to make you feel bad, he was literally a bully obsessed with you. He knew every detail about you, he knew what you liked and what you disliked
Alastor was so obsessive with you that he had threatened the entire high school so that they wouldn't get close to you and that you wouldn't even have friends. Of course, without Sunny realizing it. And also Alastor got jealous very easily any interaction with someone who wasn't with your parents or some relative he didn't know. He felt enormous jealousy. Also Alastor had you on his phone and always sent you messages every day to bother you or just to know how you were.
Alastor always sent you images about the dead deer he had hunted and their organs, Alastor was a very sadistic boy