Patna: Shoaib, the caretaker who looked after retired irrigation commissioner Harendra Prasad and his wife Swapna Dasgupta, was arrested on Saturday after police said he confessed to killing the 72-year-old woman in rage.

Harendra, he said, died after being assaulted by his wife following a dispute over money. "I saw her (Swapna) thrashing 90-year-old Harendra Prasad over some domestic issue on Thursday evening. When I tried to stop her she also attacked me. In a fit of rage I strangled her to death. As I had pushed her in the scuffle she fell on the ground and suffered injuries in the head and face," Patna senior superintendent of police (SSP) Manu Maharaaj quoted Shoaib, 55, as saying.

The caretaker claimed the couple had been fighting over money to observe Teej, a festival observed by women for the well-being of their husbands. Harendra had turned down Swapna's request to give him Rs 1 lakh.

Shoaib, originally hailing from Katihar district, had been living with the couple at the Dujra Chak house for the past 36 years. He told the interrogators that the retired commissioner died from injuries to his head and denied having killing him.

Swapna pushed Harendra forcibly for which he suffered the serious injuries, Shoaib said. "I have been loyal to my employer (Harendra) for almost four decades. I couldn't bear his being assaulted by his second wife," he told the police. "I immediately came out of the room when she fell unconscious. I revealed it to my wife Gulshan, who later went to the couple's bedroom where their bodies were lying. On getting information, the tenants called the police."

Shoaib, employed on a monthly payment of Rs 6,000, lived with his family in a room owned by Harendra. The police will submit the chargesheet against him shortly.

SSP Maharaaj, who was monitoring the investigation, on Saturday said Shoaib was arrested on the basis of scientific evidences. A bloodstained shirt had been recovered from Shoaib's room on the Dujra Chak compound, Maharaaj said. "Initially he tried to mislead the police by asserting that the stains were of paint and but the forensic report suggested it was bloodstains, which made Shoaib reveal the real story," Maharaaj added.

Shoaib said he returned with Harendra after meeting a local doctor around 7.34pm on Thursday - Maharaaj confirmed that CCTV footage at the main gate showed Harendra and Shoaib returning home at that time. "After he (Harendra) went to his room, I got busy in setting the sofa and other furniture in another room. An hour later, I heard him crying. I lost my cool when I found him lying on the floor and his wife beating him repeatedly. In a fit of rage I attacked her," he told the police.

Maharaaj said the twin murders occurred between 8pm and 9pm. "The post-mortem report is awaited," he said, adding that Harendra's body bore injuries from his wife's bangles.