Harassment in constructing own property

My name is Sugandha Mazumdar iam married and based in kolkata. My query is about my maternal property.My mother and father purchased a small school in Jamshedpur around 4 khatas in 1980 from the owner who was not able to run the school properly .My father and mother being from a teaching background executed operations of the school successfully for a long period of time due to lack of strength and growing age they decided to construct a building and accepted the proposal from a local builder.Our house has been demolished and now few local people with their relevant political references trying to stop the construction through different means they have also asked for a ransom which my father has denied.post getting scary phone calls and threats my father reported with all necessary documents to the police station where the Officer in charge showed lethargic attitude towards the matter post which my parents went to the SP Office and given and applications stating the fact.however these lawful men conterminously stated that our paper works are absolutely ok and we can conteinue the construction work but repeatedly the locals are using their political contacts to stop the work and the local Police station is proclaiming themselve to be helpless.Now there is a 144 registered by the police .I would like to know how to stop these people legally and strictly so that they get a lesson for their life and do not harass innocent people and make them face such evil illusions of our police and political criminals....Kindly help my parents are really alone and misguided by several oversmart personalities who do not wish to solve issues by the rule book ..and i firmly believe that our constitution will help my parent to come out of this permanently....kindly refer a permanent sollution so that we can construct our project.