Question about domestic violence, social worker help etc.?

Hello, I have a question. I just found out today, that my wifes nease got hit really bad on her arm and it left about an adults palm bruse on her shoulder by her step father. My nieces mother, tried to do the right thing several times to get him to go to counseling. But he is getting worse, and only acts like an inocent bystander everytime he had to go to court or counseling. They are to my understanding separated, but the husband keeps on forcing his way into the house and yells and intimditates and threathing their family. An from everything i have been told, he is even to the point where he follows her everywhere to find out what she is doing, and keeps on trying to get her mad at us for trying to help her out. Since My sister in law is like to scared to make a report, for what ever the husband keeps telling her, Can I being the uncle in law or my wife since that is her nease and the mother is her sister press charges for domestic violence against him for the abuse he does to the daughter and for my sister in law im guessing that she for sure has to be the one to speak up when he keeps on breaking into the house or can we act on her behalf to since she is to scared, and her responce to everything is i don't know what to do. I ask because the girls step father is getting worse, and everything that happens between him and my sister in law, he takes it out on her. The girl even as i speak to her somethines, her responce was not to worrie, that it is only going to last one more week, and everything points to running away from her home.Please advice as to what we can do, and who we can contact to put a stop to this persons behavior. Or im my opinion put him in jail, i already contacted domestic violence, but i know there is also a hotline but i cant find where a social worker will do a visit and investigation on the family, i live in San diego, CA so any resources you can provide i would be greatful to help my nease and her little brothers. Thanks