Bhubaneswar, Aug. 21 :    Bhubaneswar, Aug. 21:  With the recovery of a letter he wrote to his company and other evidence, it appears Durjodhana Maharana was ?haunted and mentally unstable.? Maharana is suspected to have killed six members of his family before committing suicide in Jagatsinghpur on Wednesday. Superintendent of police Lalit Das today said over telephone that Maharana, in a letter to Nalco authorities in July, explained his long absence from work saying he and his family had been ?haunted by some evil spirits.? Das said the letter was seized from the company?s office in Angul where Maharana worked and was verified by family members of the dead. Das said the autopsy report also said Maharana?s death was ?suicidal by nature? and that he was not murdered and then hanged. The death of his 14-year-old son was caused by strangulation, while other members of the family died from deep cuts on their throats with a sharp weapon, the report added. Das said the police were awaiting forensic reports to find out if Maharana had throttled his son. He said the reports would reveal whether the blood on his tunic matched that of the family members who were killed. The police also recovered a sharp, blood-stained sword from a pond adjoining Maharana?s half-constructed house in Jagatsinghpur yesterday. The sword, sent for forensic tests, was found after firemen pumped out the water. Das said some amulets and puja materials were also found in a pot that was buried alongside the sword in the pond. He said this indicated Maharana had engaged in witchcraft. The officer said interrogation of his relatives revealed Durjodhana Maharana had an illicit affair with his sister-in-law. He said the man had become ?mentally unstable? since the woman had committed suicide a year ago in the same pond from where the sword was recovered. The police are investigating if Maharana had undergone any mental treatment at Nalco hospital or elsewhere. Shortly after his sister-in-law committed suicide, Das said Maharana had turned to black magic after his house caught fire ?mysteriously.? He said a local witchcraft practitioner (ojha) told the police that Maharana had stayed in touch with him after he had suffered burn injuries in the fire in his house.