[Lauv Keiko]

I suppose that woman needs to get a straight jacket, kagu is right.
I'm sorry you have to deal with this, I think it's best you find out first if he's okay, he's safe somewhere or just as far as he can from his abusive mom.
Then, as much as possible, block the accounts but never delete any chat history and such.
It's best to contact the police because it might go out of hand soon.