Investigation in the murder of Ryan International School student Pradyuman Thakur is on the right track, the Gurgaon police said today, adding there was also a huge "criminal culpability" on part of the school in the crime. Debunking reports of the involvement of a third person in the murder, Gurgaon police chief Sandeep Khirwar told NDTV today that he was "200 per cent sure" that the investigation was on the right track and promised to file a chargesheet in the case before the stipulated time of 90 days.