Why Criminal got Bail in case of Attemt to Murder

Sir/Madam, Myself Meghnath and my family staying as a tenant at UshaRani Roy’s (Wife of Gopal Chandra Roy) house since 1999. After she expired (on the year 2011) ownership of that property on which we are staying had been transferred to her youngest son Subhash Roy (Son of Gopal Chandra Roy). From then Shubhas Roy is the person to whom we were paying the monthly rent. Suddenly from May, 2015 Subhas Roy and his family members: Sashikala Roy (Wife of Subhas Roy), Biswarup Roy (Son of Subhas Roy), Rohini Majumder (Daughter of Subhas Roy, wife of Sudev Majumder) are trying to take out us from the possession with injustice. Several false cases are placed against us. Some of those cases are disposed with the help of our advocate with the evidences. We have applied for Rent Control Case (Case no. 35/2015 Under Baruipur S.D.O.) also. Till now there is no positive response from the SDO. They have already cut down the electricity and tried to block the way front of my house by digging deep. Day by day they are disturbing us with bad languages and trying to harm us. On 20th August Rohini Majumder, Shubhas Roy, Biswarup Roy and Subhas Roy has beaten my mother badly, we have filed a FIR (no. 1750 dated 26.07.2016). We have several times reported to local police station and done the GDs. Last Monday Sashikala Roy (Wife of Subhas Roy) and Biswarup Roy (Son of Subhas Roy and Sashikala Roy) has tried to murder my mother. She bravely succeeded to escape from there. From the injury it can be clearly seen that left eye could be damaged. If she cannot succeed to escape from there she would be dead. I have seen my mother in heavily bleeding situation. We have gone to the local Municipal Hospital for the treatment and filed an FIR (no. 2040 referenced GD no. 523 dated 05.09.2016) for this at Sonarpur Police Station in presence of IC Paresh Chandra Roy. He had promised for all the co-operation. Investigation Officer Gopal Chandra Saha was assigned for this case. On very next near 1 PM the investigation officer had come to our place. Criminals (Sashikala Roy and Biswarup Roy) was not there at home. The officer had assured me that we will get justice and leaved that place on that day. After this day on Wednesday afternoon all the members of Subhas Roy’s family had come back to their home. Later we get to know they have surrendered to Police Station and living freely. I cannot understood the process. My mother would have died on Monday. I have a question in my mind that why they would be bared like this? I think this is not done properly, we are not given proper justice. If this the way of justice then they would harm us in future also. I am feeling very helpless at this moment. Please help me further if there is any way to go with it.