They initiated the case against several unidentified suspects on Monday, said Dirai Police OC KM Nazrul.
Tuhin, the son of farmer Abdul Basit, was found dead in the Kejaura village under the Upazila’s Rajanagar Union in the early hours of Monday.
His family discovered Tuhin’s mutilated body hanging from a tree next to a mosque near their home after he went missing late at night.
According to the police, two knives were stuck in the boy’s stomach while his ears and genital had been dismembered.
Later, the district’s Additional Superintendent of Police Mizanur Rahman said a few members of his family were involved in the murder.
Tuhin’s body was subsequently handed over to his loved ones and he was buried later in the evening.
Police, however, declined to comment when asked why charges were not brought against any family member despite insinuating their involvement in the incident.