Dear Zoraiz and Aiza,
When a person acts abnormally, it means he should be treated in a different way (psychologically). Try to solve the problem without showing any reaction. Get closer to him whenever you meet him, say compliments (salam), smile and shake hand. He may sometimes show a rude behaviour with you too but later you will see he is going to behave in a better way. You can help him in his studies so he would be grateful to you and will never tease you InshaAllah.