The family were last seen at a gathering with friends last Monday
Detectives believe a businessman killed his wife and daughter before setting fire to their mansion and then killing himself, police have said.
West Mercia Police confirmed that Christopher Foster's body had been identified after being found at Osbaston House, Maesbrook, Shropshire.
Tests are still being carried out on the third body, but it is believed to be his 15-year-old daughter Kirstie.
His wife, Jill Foster, 49, died from a gunshot wound to the head.
Det Supt Jon Groves said: "Detectives investigating the arson and murders at Osbaston House in Maesbrook in the early hours of 26 August believe Jill and Kirstie Foster were killed by Christopher Foster."
Mr Groves said that CCTV showed a man "clearly believed to be Foster" walking from stables with a gun and moving a horsebox in front of gates at the property.
Police explain why they believe Mr Foster was responsible
He said the CCTV footage, from a camera at the property showed Mr Foster "with what appears to be a rifle in his hands".
"It also shows outbuildings going up in flames around the same time and a large horsebox being driven down the driveway, blocking the main gates to the premises.
"A man, again believed to be Mr Foster, is seen to get out of the vehicle and apparently shoot out two of the tyres."
A cause of death for Mr Foster, who was 50, has still to be established. His body was identified from dental records on Tuesday afternoon.
Police said a rifle discovered near the couple's bodies had been identified as belonging to Mr Foster.
Mr Groves added: "The location of the third body found on Sunday suggests that it is Kirstie Foster but further tests are needed on this body to confirm identity."
The bodies were found in different parts of the house
Mr Foster amassed his fortune developing insulation technology for oil rigs.
But court documents show his company, Ulva Ltd, had gone into liquidation and owed about £800,000 in tax. It also faced legal action from one of its suppliers for thousands of pounds.
Mr Groves said he had taken the decision to reveal details of the police inquiry in an attempt to end speculation which has surrounded the case, and to give early answers to the local community.
"This is a very complex and unusual case and around 100 officers and staff have been working hard to establish the circumstances leading up to the fire," he said.
He said the investigation itself was "far from over" and the examination of the site would continue for several days at least.
Martin Timmis, of Shropshire Fire and Rescue Service, said an investigation was being carried out to find exactly how the fire was started.
"It's clear from what we have seen with the aerial footage that there is likely to have been more than one seat of fire," he said.
Farrier Ian Coe, who fitted shoes to the family's horses, remembered Mr Foster differently.
"I've seen and read in the papers and on the news and it's a different family, a different person, to the one I knew," he said.
"It doesn't add up at all. You take people as you find them and the people I knew and met are not the same ones that I'm reading about.
"They loved the life, the horses, the dogs - Jill, Chris and Kirstie - that was their life."
Mr Coe described the family as "very friendly, very bubbly, outgoing, a pleasure to be around".
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