father going insane.

Hello , and i am in need of desperate help. And i mean really desperate. Last year we discovered that my father was having an extra maritial affair with another women who is married but does not stay with her husband( not divorced either). We found a voice note from that woman in my father s cell phone. Before 4 yrs every thing was going perect in our house but den he started to come late in home didnt ate anything made by my mom. Started fighting with mom. After that we found out the voice note and came to know everything. When he was caught , he started making all sorts of allegation that my mom made up all this , she is trying to frame him and all nonesense. 2-3 months went that way with fights between them evry night. My dad used to eat at his new wifes house. He came to find the apt of that woman. When we asked the watchman of that apt who was that woman'e husband they told my dad's name . We came to know that the woman knows that my dad is already married. The problem is that my dad is a policeman. And a corrupt one. He then threatened my mom in killing her. My mom went to the station to file a complaint against him. Bt d inspector denied to file the f.i.r as he was friend of my dad and said that he will take to him. If an f.i.r was filed his job would get compromised. So my mom didnt do anything. 4-5 months thing went normal. But again recently he tries to start fight with my mom. But my mom just ignores him. He uses very filthy language describing her. He tries to provoke her. My moms cousin who is an advocate was helpng my mom but then we came to know that she was on my dad s side. She was just pretebding to be on our side. Yesterday he came home and started a fight . In fear my mom n my younger brother locked themselves inside their room. And he was constantly telling them to open the door and was giving them threatning. The problem is that my dad is playing his game good. Being a policeman he has lots of contact and can do aything. Even bying witness and may file a false complaint against us. Yesterday he was threatning to file a criminal conplaibt against us. The problem is i am studying outside and cant go to my native very often due to which i feel helpless. But a good thing is that we have that woman s voice recording and infact d voice recording of my dad threatning us. I need aome suggestion please . What should my mother do.