Brother harassing mother to transfer her property what she can do

We had pooled money among siblings and parents (senior citizens) savings and purchased a commercial property. However it was registered in one brother's name only. Later jointly registered with my mother in mutual agreement that it would be family business as all contributed for it (proof:bank statements and mortgage papers of ancestral property. Now the brother in whose name the property was registered is staking full claim and also harassing my mom to transfer her share back in his name. He claims that since it was registered in his name it belongs to him only. He disrupts work by getting anti social elements from outside and giving freebies from our place, randomly keeps withdrawing money from the current account/ business account (as signatory for the bank), threatens all of us and also our mother now claiming that he was cheated into getting it jointly registered with my her. My mother has taken seriously ill due to mental stress and physical health problems. Please advise. what can be done ?