The investigation into the gruesome quadruple murder of a retired teacher and three members of his family in Rangpur has been transferred from Kotwali Police Station to the Detective Branch (DB) of police for a more intensive probe.

"The investigation has been transferred to DB for a more intensive investigation into the case of four murders and speedy charge sheeting," Sanatan Chakraborty, Deputy Commissioner of Police (DB) of Rangpur Metropolitan Police (RpMP), told a local media on Tuesday.

Inspector Md Zinnat Ali, Officer-in-Charge (OC) of RpMP’s Detective Branch, has been appointed as the new Investigation Officer (IO) of the murder case, which was filed with Kotwali Police Station on Sunday.

The initial IO of the case, Inspector (Investigation) of Metropolitan Kotwali police station Milan Chatterjee, came to the DB office on Monday afternoon and handed over all case documents to the new IO.

Following the handover, both investigation officers visited the crime scene at the home of teacher Ganapati Chakraborty Jewel in Machhuapara, under Ward No 24 of Rangpur City Corporation area, where the former IO briefed Inspector Ali on the progress and findings of the investigation so far.

The victims—Ganapati Chakraborty Jewel (65), a retired teacher of Rangpur Zilla School; his wife Pritilata Chakraborty Bhola(50); their daughter Agami Chakraborty Prarthi (25); and their son Ayush Chakraborty Priyam (12)—were strangled to death at their residence. Police recovered their decomposed bodies on Saturday night.

Following autopsies at the Rangpur Medical College Hospital morgue on Sunday evening, the bodies were handed over to relatives and subsequently cremated at the Dakhiganj crematorium later that night.

Addressing the motive behind the killings, RpMP Commissioner Mohammad Abdul Mabud previously stated that the retired teacher, along with his wife, daughter, and son, were murdered when Ganapati Chakraborty tried to stop the perpetrators from consuming Yaba tablets on the rooftop of their house.

Police arrested two neighbours in connection with the crime, identified as Mugdha Das (23) and Siddhartha Das (19) both residents of the city's Machhuapara area.

On Sunday night, the two accused gave confessional statements under Section 164 of the Code of Criminal Procedure before Chief Metropolitan Magistrate Court Judge Md Rafiqul Islam. After recording their statements, the court sent both Mugdha Das and Siddhartha Das to jail.

Reaffirming the focus of the ongoing probe, DC (DB) Sanatan Chakraborty told the media that case IO Inspector Zinnat Ali has officially taken charge and has already initiated the DB's investigation.