Police on Saturday arrested a 64-year-old man from Bihar’s Munger in connection with the double murder of his sister and her husband in Birbhum’s Labhpur on September 25.

Purnendu Chatterjee, 76, a retired teacher from West Burdwan’s Asansol, and his wife Swapna, 68, a retired rail employee, had been found bludgeoned to death in their bedroom.

The arrested person, Mukul Mukherjee, was Swapna’s brother, the police said.

“This person (Mukherjee) was the mastermind behind the murder of his sister and her husband for property-related reasons. We had earlier arrested two men who had committed the crime,” Shyam Singh, the Birbhum police chief, said.

Earlier this month, Debnath Konai and Somnath Mondal had been arrested in connection with the murders. During interrogation, Mukherjee’s name had come up.

There was a dispute between Swapna and Mukherjee ever since their mother gifted Swapna the entire family property, the police said.

“Mukherjee bore a grudge as he felt he had been deprived of his share. So, he had planned revenge. Mukherjee contacted Debnath and Somnath to carry out the murders. These two held a grudge against Swapna and her husband,” an officer said.

A Bolpur court has sent Mukherjee to seven days’ police custody.

The bodies had been recovered after the couple did not respond to repeated phone calls of a neighbour. The couple’s son, Kallol Chatterjee, a travel agent in Asansol, had reached the Birbhum village home on being alerted.