Four members of the same family killed themselves after leaping from their seventh-floor apartment in a suspected "collective suicide".
Local police investigating the tragic mystery said the French family jumped one after another from their apartment in the Swiss town of Montreux.
The family appeared to be fervent conspiracy theorists and hoarded food in their apartment, they added.
The tragedy happened in the town on Lake Geneva last Thursday, reports the Mirror.
Only a 15-year-old boy survived the tragedy. He now remains in a coma in a stable condition in hospital.
The Vaud regional police announced that their findings "make it possible to rule out the intervention of a third party and suggest that all the victims jumped from the balcony one after the other".
They are currently working on the theory of a collective suicide, they said.
A 40-year-old man, his 41-year-old wife, her twin sister and the couple’s eight-year-old daughter along with the boy, all took their own lives.
France's Journal du Dimanche newspaper said the father, Eric David, grew up in a wealthy part of Marseille and even attended one of France’s most prestigious schools, the Ecole Polytechnique.
The twin sisters, Nasrine and Narjisse Feraoun, grew up in a family of five children who were all educated at the elite Lycee Henri-IV in Paris.
The mother was a dentist and her sister an ophthalmologist and the newspaper also said the twins were granddaughters of Algerian novelist Mouloud Feraoun.
Police said that the family were “withdrawn from society” before their suicide.
Two officers knocked on the apartment door at 6:15am local time, asking to speak to the dad about his son’s homeschool arrangement.
However, after a voice asked who was at the door, they said nothing more and officers, unable to enter the apartment, left.
Then, less than an hour later, just before 7am, all five leapt from the balcony within the space of five minutes.
Police could find no evidence of a struggle, seemingly confirming that all of them jumped of their own accord.
A step-ladder was also found on the balcony, where they jumped from.
Police said: "Before or during the events, no witnesses, including the two police officers present on the spot from 6:15 am and the passers-by at the foot of the building, heard the slightest noise or cry coming from the apartment or the balcony.
"Technical investigations show no warning signs of such an act."
They added that since the start of the pandemic, the family had become increasingly interested in “conspiracy and survivalist theories”.
The family lived in almost complete self-sufficiency, cutting off the outside world.
They have amassed a stockpile of food, which took up most of their living space.
Only the mother’s twin sister worked outside the home, with neither the mum nor eight-year-old registered with local authorities.
Police added that the evidence suggested the family feared authorities interfering with their lives.
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