Mental Torturing & not allowing to finish work for property boundaries to my Father (Senior Citizen)

Sir, My father having 69 years of age, required to complete the works of boundaries of his property (which is two meter height than the second party property level), there are two parties are sharing our boundaries, First party don't have any issues and second party claiming a 3 foot pathway is existing there. If they required a pathway, the other side of the property having another pathway. My father started the work and reaching to complete (Total length 42 meter and completed works of 40 meter) suddenly the second party came and objected by creating shouting like threatening and all, then we stopped the work for temporary, they claimed that, there is 3 foot pathway. As per our records about 50 years' there is no such pathway. Their main motive to mentally torture us and get a pathway. So we have filed a Caveat and a petition to our nearby Police station, they inspected and asked other party to submit the reason for objection and provide the valid documents against their claim. Now 20 days finished and still they are not able to submit the documents. * In this situation what we can do from our side? * A Senior Citizen, my father can file any other case against them? * I am an NRI, do I have to file any case against them to show that they are mentally torturing my father and he is senior citizen and his health issues. * I feel Police taken this case as simple a boundary issues. Please advise. * There is no possibilities of pathway in the existing 2 meter height area and their property. I hope you can clear the above mentioned matter. Thanking you Saveesh