Police on Thursday morning arrested the son-in-law and a contract killer he had hired to murder the retired army man and his wife at their home at Habra’s Tunighata-Mandalpara in North 24-Parganas early on September 16.

The police claimed that Bunty Sadhu, 32, had planned the murder of his parents-in-law Ramkrishna Mandal, 58, and Lila Mandal, 51, in a manner that would not bring him under suspicion.

Based on a complaint filed by the family members of the deceased, the police had earlier arrested Tanmay Bar, the estranged husband of the couple's niece, who had on a number of occasions threatened to eliminate the family after his wife filed for divorce. But probe revealed Tanmay had no role in the murder.

Speaking to mediapersons on Thursday, superintendent of Barasat police district Avijit Banerjee said: "It’s true that we had begun the probe on the basis of the FIR that named Tanmay Bar as the accused. But during Tanmay’s interrogation it gradually became clear that he had no role in the murder and the couple's son-in-law Bunty Sandhu surfaced as the accused."

Banerjee said that Bunty, who runs a grocery store in Habra, planned the murder of his parents-in-law apparently to grab their property after they refused to shell out Rs 8 lakh he had demanded to clear his “debts in the market”.

On Wednesday night, the police picked up Bunty and contract killer Ajay Das, who was allegedly lured into killing the couple on a promised payment of Rs 10 lakh. Bunty allegedly told Ajay that he would pay after getting control over his parents-in-law’s property.

“It’s bizarre that the supari killer had carried out the murder on credit,” said a police officer.

Banerjee said it was Bunty who deliberately floated Tanmay’s name as the killer and got the family members of the deceased to name him in the FIR. As Bunty was present at the time of the crime, he used Tanmay’s name to mislead the investigation, Banerjee added.

A police officer said during interrogation, Bunty confessed that he had hired Ajay and gave him directions about how to sneak into the house of Ramkrishna and Lila after landing on the terrace on September 16. Ajay shot them from close range in the presence of Bunty. As the entire incident happened around 3am, family members could hardly identify the killer and Bunty saw this as an opportunity to frame Tanmay.

An investigating officer said that some crucial leads provided by Tanmay during the interrogation helped cops crack the case. “It was Tanmay who told us that Bunty had serious differences with his parents-in-law ever since they refused to pay him Rs 8 lakh,” an investigating officer said.

“We also came to know that Bunty had got in touch with a person to buy the firearm used in the crime. As circumstantial evidences substantiated Bunty's role in the murder, we picked up him for interrogation. He tried to mislead us, but eventually broke down and confessed his role in the murder," a sleuth said.

Sources said Bunty had married the couple's younger daughter a few years ago. He had run up huge debts in the market as his grocery business was not running well and needed money to clear his debts.

"During interrogation Bunty disclosed that he requested Ramkrishna to give him Rs 8 lakh to clear the debts. Ramkrishna refused. Bunty’s effort to convince his mother-in law did not work either. This led Bunty to plan the murder of the couple. He thought that in the absence of the couple he will be able to grab the property as the husband of their only surviving daughter,” Banerjee said.

The couple’s elder daughter had died a couple of years ago. When asked if the couple’s younger daughter (Bunty's wife) had any role in the murder, the senior policeman said: “It will also be examined.”

Both the accused persons were produced before the ACJM court in Barasat that ordered them 10 days of police custody.

The police will soon begin a process to exempt Tanmay of the charges and drop his name from the case, the SP added.