The two detained suspects were identified as Mughdho and Siddhartha.

Rangpur Metropolitan Police Commissioner Mohammad Abdul Mabud told The Daily Star during a briefing that the two suspects allegedly entered the rooftop of Ganapati Chakraborty's house through an adjoining building and consumed yaba there on Thursday night.

The retired teacher reportedly went to the rooftop after hearing noises and questioned the men about their presence.

Police said the suspects allegedly strangled Chakraborty to prevent him from identifying them. After hearing the commotion, his wife, Pritilata Chakraborty, 50, went upstairs and was also allegedly strangled to death.

Their daughter, Agami Chakraborty Prarthi, 23, and son, Priyam Chakraborty, 12, were also killed during the incident, police told The Daily Star.

Police said the family did not appear to have any known enmity with anyone.

Subir Chowdhury, in-charge of Rangpur Metropolitan CID, had earlier told The Daily Star that household belongings were found scattered and in disarray, suggesting that robbery could have been a motive.

“The household belongings were found scattered and in disarray. For now, it appears to be a robbery. However, nothing can be confirmed until the investigation is completed,” he said.

Sanatan Chakrabarty, deputy commissioner of Rangpur Metropolitan Police and head of the Detective Branch, told the newspaper that the bodies had been sent to the morgue of Rangpur Medical College Hospital for autopsies.

“Initially, we suspect that they were strangled,” he said, adding that the killings may have taken place sometime between midnight on Thursday and the early hours of Friday.

Puja Chakraborty, Pritilata's younger sister, told The Daily Star that she had last spoken to her sister on Thursday afternoon.

She said the mobile phones of all four family members had remained switched off since that night.

“We came to Daspara on Saturday night after finding their phones switched off. The main gate of the house was locked and all the lights inside were off. Police later arrived, broke the lock and entered the house, where they recovered the bodies,” she had earlier told the newspaper.

“I cannot understand who killed my sister and her entire family, or why and when it happened. My sister's husband was a very good man. He had no enemies. They had built a new house in Daspara and were living there,” she said.