The couple's four-year-old daughter, named locally as Zeena, was found alive in the BMW estate underneath the bodies of her relatives around eight hours after the massacre, which also saw a passing French cyclist, Sylvain Mollier, 45, shot dead.
The al-Hillis' seven-year-old daughter, believed to be called Zainab, was in a medically induced coma in Grenoble University Hospital after being repeatedly beaten around the head and shot in the shoulder in the attack.
Three of the four who were killed were shot in the middle of the head, but the man investigating the spree played down suggestions of "professionalism" in the attack. Public prosecutor Eric Maillaud told a press conference: "I won't say it was professional, what I will say is it was tremendous savagery. And what is certain is that somebody wanted to kill."
But one of the family's neighbours in the upmarket village of Claygate in Surrey said he was going to alert police to something Mr al-Hilli said to him before travelling to the Le Solitaire du Lac campsite in Saint-Jorioz, close to the Swiss border.
Jack Saltman said: "I know one little thing which I am not prepared to speak (about) at the moment. I will tell the police about it. It was something Saad said to me before he went, but at this stage I do not feel I can disclose that, but I will tell the police exactly what he told me before he left."
The powerful BMW was discovered surrounded by spent bullet cartridges in a car park near footpaths on the outskirts of a forest near Lake Annecy, a picturesque region popular with tourists. A British cyclist, a former RAF serviceman who had been overtaken by the French rider, discovered the grisly scene in a quiet car park, said Mr Maillaud.
The four-year-old lay undiscovered as police waited for forensic experts to arrive at the scene from Paris. She was found "terrorised, motionless, in the midst of the bodies" after fellow campers at a nearby site told officers the family had two children, said Mr Maillaud.
Mr al-Hilli was known to the security services and was put under Metropolitan Police Special Branch surveillance during the second Gulf war, it was reported in the Daily Mail. A Scotland Yard spokesman said they could not comment because Mr al-Hilli had not yet been formally identified.