He said the four year old girl who was found alive in the vehicle, eight hours after the scene of the crime was sealed off, has been examined by a psychiatrist and a nurse. He said she was experiencing profound sadness and trauma.
It is thought that the cyclist who was shot dead accidently entered the scene of the crime.
He was a local man called Sylvain Mollier, who was 45 years old.
His wife contacted the gendarmerie when her husband failed to return home after a bike ride, and his photograph matched the identity of one of the victims.
Prosecutor Eric Maillaud said the driver, the elderly lady and the dead cyclist had all received bullets in the head, but that it was not possible to determine the exact cause of their deaths until autopsies are completed.
The prosecutor said there were traces of 15 bullet shots and investigators are now analysing the spent cartridges.
The body of the younger woman, the child’s mother, has not yet been removed from the car.
The cyclist who reported the crime to the police is thought to have arrived just minutes after the shootings, and is a former member of the British Royal Air Force.
There were lots of bags in the boot of the car, but Maillaud said it was not clear or not whether the family had packed to leave the campsite where they were staying.
The prosecutor said it was unclear whether the dead father of the girls was the owner of the car, and he was still unable to confirm reports that the father was called Saad al-Hilli.
The owner was 50 years old and born in Baghdad but had British citizenship and a home in Claygate, in Surrey, just south of London, said the prosecutor.