DD and DH returned home at just after 6, we sat down and had dinner together and I told that if he hits her again she needs to tell me straight away and I will be phoning the police. And I also told her that if she wants counselling then it will be available to her, after the holidays I will also be contacting to school to ask about their student support etc.
DS comes home at 8 (1 hour after I told him to come home)
I told him that he needs to stop with his disgusting behaviour towards DD, and also the way he speaks and treats me, because it is not acceptable to treat anyone like that and I will be phoning the police the very second he next lays a finger on DD because he is mentally abusing her, and she is scared in her own home, and she will not be the one leaving if his behaviour continues.
A lot of shouting ensued (from DS) and he tried to storm out, but DH blocked his exit.
I continued to speak to him reiterating what I said already.
He then stormed up to his room, all devices removed so he can sit in there and stew.
Hopefully he has realised the severity of his actions and will not be doing it again, but only time will tell.