My brother harasses my mother

I am married female (30 years) staying with my husband. My father died 20 years ago. My mother (55 years) stays with my brother (24 years) in another city. The house where they stay is in my father's name. My brother constantly threatens my mother about leaving the house. Breaks the things in the house. Doesn't listen to anyone. My mother has got a very critical heart disease and is told by doctors not to take any tension or stress at all. And to take as much rest as possible. But my brother doesn't let my mother take any rest. He keeps shouting at her if the house isn't cleaned, or the dinner is not ready. He doesn't do any work in the house. He spends all his time on the phone or with friends. Doesn't even get a glass of water by himself. I have tried to bring my mother to stay with me, but she doesn't want to leave the house or my brother. I have also tried to make a police complaint against my brother but my mother threatened me that she will kill herself if I called the police. If I say something to by brother, he says he will kill himself, leave the house, etc. It is like emotional blackmail going on everywhere. My mother starts shouting at me if i tell by brother anything. But I can see her health deteriorating slowly due to all the mental and physical strain. What can I do? I feel helpless.