Forcefully dispossessed

It was improper that the buyer took law into his hands when the civil suit is pending. You may move appropriate application before the Court in consultation with your advocate.

The important question is: WHEN DID THIS HAPPEN?

If it happened very recently, you can approach a Criminal Court to throw him out. You must approach the Criminal Court within six months from the date you lost possession i.e. forcefully dispossessed. I hope you already lodged a police complaint. If not done, please do so immediately. It will play an important role in this matter. Please pursue this option without wasting any further time. This option will not work, if you take more than six months to lodge police complaint and initiate criminal proceedings. Criminal Courts can intervene only within the first six months. Not later. This remedy will be quick if you know a good criminal lawyer or a good lawyer who is good in both civil and criminal proceedings. 

You can also initiate civil proceedings. Recovery of possession is the right thing to do. Court fee is also likely to be high depending on the value of the property. You also need to pray for declaration that you are the rightful owner, because you entered into sale agreement and he paid part of the amount. It is necessary to study all the papers to decide the correct course of action. 

Please approach both criminal and civil lawyers or somebody who is good in both. 

During pendency of eviction suit and without court's order if yout brother has been forcefully dispossessed then he can Your brother should file petition u/sec 6 of specific Relief Act to get back possession before court .Simultaneously initiate criminal proceedings against prospective buyer.

Firstly this is a criminal offence for trespassing the property by the offenders, hence you lodge a criminal complaint for not only trespassing but also for the offences of damage to private property, land grabbing and criminal intimidation etc.

You can seek civil remedy too simultaneously.