Patna: A 90-year-old man and his 72-year-old wife were found murdered in their Buddha Colony residence on Thursday late evening, sending shockwaves through the state capital.

The couple's bodies were found in their bedroom with injury marks on their faces and necks. Police sources said the two were beaten up with some weapon and strangled, most likely between 8pm and 9pm.

Harendra Prasad, a retired irrigation department commissioner, owned two houses in Patna and more than 100 acres of agricultural land in Siwan. He was living with Swapna Dasgupta, his second wife, at the Dujra Chak area of Buddha Colony in a compound spread over more than 10 cottahs. Their son is a doctor in Delhi, and their daughter lives in Australia. The son has already reached Patna; the daughter is on her way.

Harendra's first wife lives in Kankarbagh with two sons who are businessmen.

A caretaker and his wife used to look after Harendra and Swapna. The caretaker, Shoaib, and his wife Gulshan used to live in the same compound.

Gulshan first came to know about the murders when she entered the couple's residence at around 9.30pm on Thursday.

Harendra's son Ravindra Prasad Sinha, who lives in Kankarbagh, said: "We came to know about the incident from our tenants. Gulshan told me that she had gone to the first floor, where my parents used to live, for some work and discovered their bodies."

The caretaker and tenants informed the Buddha Colony police and the two were rushed to a nearby private hospital where the doctors declared them brought dead.

Harendra's Buddha Colony compound has four buildings (two two-storey ones and two three storey). The compound also has single-floor houses which were given on rent, servant quarters and gardens. Sources said 54 tenants live in the compound and the couple used to get Rs 2.5 lakh per month as rent. The floor where the couple lived had only one entry gate.

Harendra's relatives suspect an insider job.

Bhanu Sarkar, a relative of the couple, said: "The criminals are not outsiders, but someone who knew that the couple lived alone."

Police have detained six persons: Shoaib, Gulshan, Harendra's driver Tej Pratap and Tej Pratap's wife, and two others.

"Prima facie it appears that someone who knew the couple had executed the incident," said Patna senior superintendent of police Manu Maharaaj. "There is no evidence of any loot; however, investigation is going on."