Police were grasping for answers as it emerged that all four victims in a mysterious killing in the French Alps targeting a British-Iraqi family were shot in the head.
The attack, which the prosecutor in charge of the case called an act of "extreme savagery", had many of the hallmarks of a professional assassination but authorities were at a loss to explain it.
"All the victims were hit by more than one bullet, by several shots and all of them were hit in the head by at least one bullet," Annecy prosecutor Eric Maillaud said late Thursday on TF1 television.
"Autopsies tomorrow will tell us more about the circumstances in which they died," he added.
Two young girls believed to be the daughters of two victims survived and were under police protection, including a four-year-old who hid beneath her dead mother's skirt for eight hours and at first went undetected by police.
Her seven-year-old sister was meanwhile in an induced coma ahead of surgery after being shot in the shoulder and suffering a fractured skull from what authorities said were "extremely violent" blows to the head.
The horrific massacre dominated the front pages of Britain's newspapers on Friday.
The Mirror ran with the headline "I'm scared", referring to a comment made by Hilli to a neighbour before leaving for his French holiday.
Popular tabloid The Sun carried the front-page headline "Where's Mummy?", the words uttered by the young survivor when rescued by police.
Autopsies were to be conducted on Friday and police in France were expecting DNA from Britain as they desperately sought clues.
"It was clearly an act of extreme savagery and it was obvious that whoever did this wanted to kill," Maillaud said.
The victims' bodies and the surviving girls were discovered Wednesday in a forest car park near the village of Chevaline in France's picturesque Haute-Savoie region, which is popular with tourists including many Britons.
Three of the bodies -- a man in the driver's seat and two women in the back -- were found inside a British-registered BMW estate car. The body of the second male victim was lying nearby.
A French police source named the dead driver as Saad al-Hilli, a 50-year-old born in Iraq and resident in Surrey, southeast England.
Neighbours said he was an engineer and identified one of the women, who was carrying an Iraqi passport, as his wife Iqbal. They identified the other woman, a 74-year-old with a Swedish passport, as his mother-in-law and the couple's daughters as Zainab, aged seven, and Zeena, aged four.
Authorities in France identified the fourth victim, a cyclist who stumbled across the scene, as local man Sylvain Mollier.
The Daily Mail website reported that the British-Iraqi man was known to British intelligence services.
Metropolitan police Special Branch officers working with the intelligence services placed the man under surveillance during the US-led invasion of Iraq in 2003, a neighbour who claimed to have hosted them told the paper.
The force later said it could not comment on the reports as Hilli had yet to be formally identified.
The Mail and Daily Telegraph both explored the possibility that the killings were the result of a family feud.
The Mail quoted family friend Zaid Alabdi as alleging the row was over the inheritance left by Hilli's father, who died a year ago.
The family had been staying since September 3 at the nearby Saint Jorioz camp site, where fellow campers reported their disappearance on Wednesday.
A veteran of Britain's Royal Air Force who has a second home in the area discovered the victims, having cycled into the car park at 3:48 pm Wednesday, Maillaud said.
As the Briton arrived in the car park, where the car's engine was still running, the elder girl stumbled towards him before collapsing on to the ground and he alerted emergency services.
He was praised by local authorities for his quick response and for putting the girl in the recovery position before emergency workers arrived.
Several witnesses reported seeing a car speeding away from the scene around the time the attack took place.
The firemen and police officers first on the scene quickly sealed it off. Under orders to leave the car untouched until a forensics team arrived, they failed to spot the younger girl until hours later.
Maillaud said the girl had made herself "completely invisible" by hiding under her mother's skirt on the back seat.
"She was clearly happy to be in the hands of investigators. She immediately asked for her mother," he said. "The only thing she would say is that she heard noises and shouts and that she was scared."
Child psychiatrists in a local hospital were looking after her, he said, defending the officers who took so long to discover her for not wanting to compromise the crime scene.
The elder girl was in hospital in nearby Grenoble awaiting surgery but her life was not in danger, he said.
Maillaud said investigators believed an automatic pistol was used and that 15 spent bullet casings were found in the area.
The killer did not appear to have fired indiscriminately, he said, as the bullets had gone only through the windows and not into the body of the car. No weapon was found at the scene.
Visiting the Paralympic Games in London, French President Francois Hollande vowed: "Everything will be done to find the killer or killers."
Prime Minister David Cameron also promised Britain would "do everything we can to help these poor children and also help the French police to get to the bottom of what happened in this clearly very tragic and awful case".
Shocked friends and neighbours of the Hilli family in Claygate, an area popular with finance sector workers commuting to London, described the victims as a "lovely" Iraqi couple who were often seen taking their children to school.
"We used to see the couple on the school run," one local woman told AFP. "They were lovely, they were very friendly people with really sweet little girls."