Norbert Falco/Le Dauphine / EPA

French Police officers cordon off the road leading to a gruesome scene where four people were shot dead near Annecy Lake, a popular tourist destination at the foothills of the French Alps.

Updated at 10:52 p.m. ET: Immobilized with fear, a 4-year-old British girl huddled for eight hours under her slain mother's skirt in a car filled with corpses in a remote area at the foothills of the French Alps — while investigators stood nearby, unaware she was there.

Thursday's discovery of the girl, apparently unharmed, heightened the drama surrounding a mysterious shooting rampage that left four adults dead and a 7-year-old girl hospitalized with three bullet wounds and skull fractures. The older girl had been "violently beaten," the Guardian of London reported.

Around 4 p.m. on Wednesday afternoon, a British cyclist cruising uphill came across a chilling scene: A BMW, its engine running, had three people dead inside. Nearby was a dead cyclist -- the British cyclist recognized him because he passed him on the road. Outside the car, a 7-year-old girl was gravely wounded and appeared to have been beaten.

The British cyclist, who, according to the Sun had been in the Royal Air Force, immediately placed the 7-year-old girl in "recovery position." He then walked around the car and broke the driver's side window to turn off the car.

The motive for these slayings remains unclear, and French authorities have not ruled out that this could be the work of a professional hitman. Three of the dead were shot in the forehead with a semi-automatic weapon -- which means the shooter had to pull the trigger for every shot. About 15 bullet casings were found near the car.

"All the possible scenarios have been images -- from the smallest, family drama," Prosecutor Eric Maillaud said, according to French media. "We have very, very few clues."

Maillaud described the slayings, in a wooded area near the southeastern village of Chevaline, as an act of "gross savagery." He said the scene found by officers was "well beyond television fiction."

Of the four dead, three were in the car, believed to be a British-Iraqi family vacationing at a campground on the shores of Lake Annecy, a popular retreat in the French Alps. The owners of the campground told investigators that the victims included two parents and a grandmother.

Investigators identified the driver of the car as Saad al-Hilli, 50, a British citizen and engineer from Surrey, England, who was born in Baghdad and moved to England in 1970, according to the Sipa news agency. Police in Surrey, a largely suburban county southwest of London, said they are talking with French authorities about the case.

Hilli is a respected member of the community, neighbors told British reporters.

"They are quite beautiful kids and so well behaved. He was an extraordinarily nice man and helpful. He was a very tactile loving father. He loved to gather the girls up and cuddle them," Jack Saltman, a neighbor, told the Guardian. "They would go running at him and he'd catch them in his arms and kiss them. He adored them. His wife was a delightful person and I can't think why anybody would want to harm them."

NBC News reported that al-Hilli worked as an engineer in aeronautics.

The eldest woman has a Swedish passport and has been identified in the British press as grandmother to the two girls.

See full coverage of this story at ITV News

The fourth victim was French cyclist Sylvain Mollier, 40, a father who apparently stumbled across the grisly murder in progress, police said. He was shot five times, at least one time in the forehead, le Dauphine Libere reported. He was on paternity leave from a job at a factory linked to nuclear manufacturer Areva after his third child was born in June.

Mollier had no ties to the British family; he was identified only after his wife reported him missing.

"A woman was worried because her husband went to cycle in this area and didn't come back home," Maillaud said. "He was just cycling in that area and got killed along with this British family."

'She was completely hidden'
French authorities struggled to explain why the 4-year-old wasn't discovered earlier and was left for hours alone in the back seat of the car.

Said Maillaud, according to France's Liberation newspaper: "Initially, a doctor determined that the people in the car were dead. He went to the bodies, determined they were deceased, and he removed himself. There were clothes, bags, and this little girl who remained rigorously still. Even with a thermal heat detector, this little girl was not detected. The doctors who approached the car could not detect this girl because she was completely hidden."

 4 slain in French Alps; girl, possible witness, survives

The car was under guard until midnight, when special investigators arrived from the Paris area and found the girl.

Maillaud said as soon as investigators opened the door, the girl emerged, smiled and reached out her arms; she spoke English but couldn't describe what had happened and was taken into police care.

The 7-year-old girl remains hospitalized. She was placed in an artificial coma but her life is not in danger, Maillaud said Thursday. Both girls are under armed guard.

The Associated Press and NBC's Isolde Raftery contributed to this report. ITV News is the U.K. partner of NBC News. 

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