my friend (14M and has self diagnosed autism) is now bullying one of my friends

yesterday I made a post asking for advice on how to end my friendship with my friend (who I'll refer to as joe) that has self diagnosed autism I believe he does have autism because he said he is far up the autism spectrum. He is no longer my friend thanks to the advice I was given but he is now bullying one of the members in my friend group and I need advice on how to stop him from bullying one of my friends