Torture by Daughter in law

HELP !!! My brother is married n has one kid. My daughter in law torture my brother who is an ARMY personnel n my parents. We are a simple middle class family. My father is diabetic n has heart problem n my mother has problem in her knees n in other organs. I witnessed this incident when I visited home because of my pregnancy. Ye morning se sham tak chala. My BHABHI threatens my brother "mai jail kara dungi, mai fansa dungi", beats him, ask him to separate from family though he lives away from his family because of his job. When my mom tried to protect my brother..She hit my mother 3-4 times, slapped her, injured her breast when she visited home. When my brother tried to stop thn she hit my brother and started hitting herself n said "ab dekho kaise fansati hu, tum sabki jindagi barbad kar dungi!!" , she even tried to drink phenyl n my brother tried hard to stop her. She is always in SELF-DESTRUCTIVE MODE to harm us. WE talked to her family immediately but her family denied "our daughter can't do anything like that!!!" She got more aggressive after knowing that we talked to her parents n attacked my mother n this time my father as well. She broke room, door, she snatched curtains to hang herself n thn my younger brother broke the room she was in. In this process he hurt himself while doing that. She broke the bathroom.. her child was crying, was scared n I kept begging "apne bache k liye shant ho jao, uska toh socho!!" But vo ek bar b rat tk apne bache k pas nahi aayi but kept fighting, screaming, yelling, breaking the thing n yelling. She called back her father n said the lies that my mother tortured her n she slapped in her defense n ye kafi time se chal rha hai. But interestingly they visit us hardly 2 times in a year. My brother is helpless n silent because of his job n reputation. He is always afraid because Indian law always supports women. He is under depression n told my mom once that someday he will attempt suicide which broke our heart. What should we do..?? HELP HELP HELP