Shalboni, Feb. 10: A woman was battered to death by her two sons as her daughter and husband looked on because they thought she was possessed by an “evil spirit”.

Police in West Midnapore’s Shalboni said Krishna Ghosh’s elder son Biplab, 28, a tantrik, had proclaimed that all her blood had to be drained out to free her from the demon.

Biplab, his brother Bikash, father Chittaranjan and sister Aparna have been arrested.

Biplab told the police he hit his mother on the head with a spice grinding stone in front of a picture of goddess Kali.

Manoranjan Ghosh, who lives next door at Tilaboni village, about 160km from Calcutta, said he avoided his elder brother Chittaranjan’s and his family because of their quarrelsome nature.

“Around 10 last night, I heard a groan from his house and peeped through a crack in their window. I saw Krishna lying naked on her back. Biplab, also naked, was sitting on her chest and battering her with a stone. Bikash, who was also without clothes, was holding her feet. Chittaranjan and Aparna were in a corner of the room,” said Manoranjan.

He nearly fell unconscious at the sight. “I recovered my self and ran to neighbour Prasanta Ghosh’s house. He, too, saw what was happening. As blood flowed from the woman’s body, Biplab shouted ‘look the devil is leaving’,” Manoranjan said.

It was Manoranjan who called the police and a force arrived around 11.30pm.

Deputy superintendent (operations) K.P. Barui said Biplab kept telling the police “don’t meddle with me”. “He tried to say a spirit would possess him soon and he would bring back his mother. Both brothers confessed to us that they had tried to exorcise their mother,” said Barui.

“Gurudev” Narayan Mondal, who lives at Omrapota village in Goaltore in the same district, had allegedly asked the brothers to exorcise Krishna, 43. “We are looking for the guru. Biplab also requested us that he be allowed to go to his mother’s body naked and chant mantras. We did not allow it,” a police officer said.

Ganja (cannabis) and a bottle of country liquor were found in the house.

The police said the brothers had consumed some of the ganja and liquor before the murder.