The key witness to a double shooting at the cottage where Boris Johnson grew up was held captive by the alleged killer before being told to flee the scene by a 999 operator.
Debbie Zurick, 56, a dog trainer who once worked for Princess Anne, is believed to have been shot dead on Saturday by her estranged husband John, 67.
The killing happened after Mrs Zurick returned to their cottage, formerly owned by the Prime Minister’s father, with the unnamed female friend, who Mr Zurick reportedly held captive during the shooting.
She then called 999 and was told to get as far away from the scene on Exmoor as possible.
Debbie Zurick, 56, a dog trainer who once worked for Princess Anne, is believed to have been shot dead on Saturday by her estranged husband John, 67
Pictured: Debbie and John Zurick with their dogs. A spokesman for Princess Anne said earlier this week Mrs Zurick ‘will be sorely missed'
She was only found by Avon and Somerset police after they used phone app what3words to locate the ‘key witness’, The Times reported.
The app divides the world into three metre by three metre squares to pinpoint locations.
Mr Zurick, who shot himself and is currently in a critical condition in hospital, had been arrested on February 5 on suspicion of drink-driving after crashing his car.
His licensed firearms were seized by police shortly after, leading police to investigate how Mr Zurick got hold of the shotgun that was allegedly used on his wife.
They have since referred themselves to the police watchdog.
A picture posted on the couple's social media showing Boris Johnson meeting their dog, also called Boris
Officers were called to the property after reports of a hearing a gunshot in Winsford, Somerset
The Zuricks bought the cottage in Nethercote Byre, where Boris Johnson had spent a large part of his childhood, in 2013.
They ran a successful breeding kennels and training school and even supplied clumber spaniels to Princess Anne.
Mrs Zurick was honorary secretary of the Working Clumber Spaniel Society, of which the royal is president.
A spokesman for Princess Anne said earlier this week Mrs Zurick ‘will be sorely missed’.
The Prime Minister’s father, Stanley Johnson, 79, said: ‘I and all my family are stunned and saddened by this tragic turn of events and pay tribute to... Debbie.’