An elderly couple believed to be William and Patricia Wycherley were both shot before being buried in their back garden, police have said.
A spokeswoman for Nottinghamshire Police said: "Following an examination of the remains, discovered in the back garden of a house in Blenheim Close, Forest Town, a Home Office pathologist has determined that both people died as a result of being shot."
The remains of the couple were found in the garden of a house in Blenheim Close in Forest Town, Mansfield, on October 9.
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Formal identification has yet to be confirmed, but Nottinghamshire Police believe the remains are that of Mr and Mrs Wycherley, who lived at the house in the 1990s and, according to neighbours, disappeared in 1998.
Their daughter Susan Edwards, 55, and her husband Christopher, 57, were arrested at St Pancras International railway station in London on Wednesday evening on suspicion of their murders, though police have refused to confirm the identities of the pair.
They continue to be questioned by detectives in relation to the deaths as police revealed cause of death had now been determined.
Mr and Mrs Wycherley moved into the house in 1987.
A murder inquiry was launched after the bodies were unearthed in the back garden of the semi-detached house following a tip-off to the police.
Officers have said Mrs Wycherley is believed to have been born in Fulham, west London, and would now have been 79. Her husband would have been 100.