THREE of the four victims killed at a French Alpine beauty spot were shot in the middle of the head, prosecutors said today.
The family including parents, an older woman and two children were found in a bullet-riddled BMW near Chevaline in France.
The owner of the car was named as Iraqi-born Saad Al-Hilli, 50, who lived in Claygate, Surrey.
Mr Al Hilli is understood to have been the secretary of a Wiltshire-based aerial photography company, AMS 1087, since 2007.
The woman, believed to be the mother of the two girls, was reportedly 50 years old while a 77-year-old Swedish woman was also killed in the car.
They were discovered by a French cyclist named as Sylvain Mollier, a father-of-three in his 40s, who overtook a British cyclist on the approach to the crime scene yesterday afternoon.
The second rider, a former serviceman in the RAF, then raised the alarm after finding the bloodbath.
Eric Maillaud, the Annecy prosecutor, confirmed today that the French cyclist, the man and the older woman were all killed by bullets to the head.
Detectives discovered 15 spent bullet casings around the car, which was locked and the engine running when it was discovered.
The body of the younger woman remains in the BMW and a cause of death has not yet been established.
Speaking at a press conference, Mr Maillaud described the killings as "heinous" as more details about the discovery of the youngest child emerged.
A four-year-old girl was found to be missing after police spoke to campers at Le Solitaire du Lac campsite in Saint Jorioz.
She was eventually discovered hiding beneath her mother's legs in the car where she had remained for up to eight hours.
Mr Maillaud revealed she was being cared for at a psychiatric hospital and had spoken briefly about what had happened.
A seven-year-old girl, thought to be her sister, was found injured next to the car and was taken to Grenoble Hospital with a fractured skull. She had been placed in an artificial coma and had undergone surgery, Mr Maillaud added.
Twitter: William Hague - Terrible, tragic shooting in France. British Embassy team on the scene. Our thoughts are with the young girls who survived and the family
He said she was not yet out of danger after suffering "extremely violent contusions of the skull" and a bullet "in the shoulder".
"It was hard on this little girl," he said.
"Our role is to ensure that the investigation is not polluted. Things must be done in a methodical way, otherwise we may never find the perpetrator of these crimes."
He said the attack was "particularly out of the ordinary".
Mr Al-Hilli was identified as the owner of the car from its registration plates but detectives were unable to match the woman to the photograph in a passport left at the campsite.
"We do not absolutely know for what reason these people were killed," Mr Maillaud said. "Three of the four people killed were hit by shots to the head. Only autopsies will say more. They are planned Friday."
"It was clearly an act of extreme savagery and it was obvious that who did this wanted to kill," he added.
Paying tribute to the British cyclist who stopped and gave first aid to the older girl, the prosecutor added: "The way the cyclist acted, he should be saluted. He is a former Royal Forces man."
A senior police source said the terrified youngest child had only been found at midnight when witnesses at Le Solitaire du Lac campsite told detectives the family had two children, not one. Only then did they "break with protocol" and open the doors to find the girl.
He said she was very small and young for her age, and had not appeared to have understood what had happened to her family.
Along with her sister, who was in hospital after being beaten and left for dead, he said they were "key witnesses" who were being heavily guarded.
The source also dismissed suggestions the attack may be linked to two attempted car-jackings, describing the massacre as a "very particular modus operandi" in a spot popular with tourists.
The family was believed to have been coming to the end of their holiday, having arrived in France at the end of August.
Mr Maillaud said that when forensic officers began a detailed examination they found the girl who had remained hiding, silently, in terror, for up to eight hours.
"When the investigators got into the car they discovered a little girl, who was frozen still and uninjured," he said.
"She could not tell the difference between the good guys and bad guys. She spontaneously began to smile and speak in English when the policeman took her in his arms and pulled her out of the car."
He added: "The little girl spoke English. She had heard the noises, the cries but she couldn't say more, she is only four years old."
Police are unsure when they will be able to question the girl, who was in a state of shock.
Kara Owen, the deputy British ambassador, is in Grenoble at the injured girl's bedside in hospital before going to the scene of the massacre at Chevaline.
Officers said the younger girl had remained undiscovered for eight hours "due to procedure".
The source explained: "The crime scene was kept frozen until forensics experts arrived from Paris during the night.
"This meant that the dead bodies had to remain in the place where they fell. The little girl was well hidden under her mother’s legs, and clearly was in a state of shock."
The identity of the victims "remains to be verified", Mr Maillaud said.
The site reported a family including parents and a grandmother missing.
One woman, who was staying at the same campsite, said: "I saw the two women yesterday with the two little girls collecting apples. Everything seemed normal, but I didn't know them.
"It was the first year that they had been seen here. It is terrible. The atmosphere is heavy, nobody is speaking."
Mr Maillaud said the main theory was that the attack was a crime gone wrong but said "a family drama cannot be excluded".
"The owner, the driver of the vehicle, is established as a British citizen. For the others, presumably his family, it remains to be seen," the prosecutor said.
"He had left his passport details at the Saint-Jorioz campsite."
Later, it emerged there had been two attempted car-jackings by an armed gang 50 miles away on the same night. Police were investigating links between the attempted thefts and the shooting.
A police source told France's Europe 1 radio: "Current theories are either that the family were the victims of an armed robbery or that they disturbed a drug deal taking place."
The shooting happened in a tree-lined car park near the picturesque village of Chevaline, a popular destination for holiday-makers and tourists.
The Foreign Office said that the British Embassy's deputy head of mission in France was at the scene of the shooting.
"She is liaising with the local authorities and police to get more information," a spokesman said.
Didier Berthollet, the mayor of Chevaline, told a local newspaper that “the victims were not from the village”.
He added: “We have never seen such horror on our doorsteps before. The police have interviewed everyone in the village hoping to find a witness. There are only 70 homes, so it didn’t take them long.”
Earlier this summer the Foreign Office warned British tourists driving on the Continent that they were regarded as “easy targets” by gangs which staged accidents to make them stop before robbing them. A French police officer said: “It’s the time of year, the thieves go for tourists who they see as rich.”
France recently tightened its laws on illegal firearms amid a worrying rise in the use of guns by criminals. In July a gunman using an assault rifle shot dead two people and injured five at a nightclub in Lille after being turned away.
In March, Mohammed Merah, who claimed to be linked to al-Qaeda, killed four people at a Jewish school and three soldiers in southern France. He was killed after a 32-hour siege in Toulouse.
Henry Samuel and Donna Bowater Telegraph.co.uk