Annecy gun victims 'were UK tourists':France shoot
The bodies of two women and a man were found in a British-registered BMW car. The fourth person killed was a cyclist.
A prosecutor said the identity of the man - described as the father - had been "almost certainly" established.
Two young girls were found alive, one eight hours after the deaths. The other is in a critical condition in hospital.
The fourth person killed was a cyclist, said by officials to be a resident of a neighbouring area.
The area has now been sealed off by some 60 police, who have started a criminal investigation into what they are calling a multiple murder.
One girl was initially reported to have died of her injuries but AFP later said Mr Maillaud, who had announced her death, had issued a correction.
He now says the child, thought to be aged eight, is in a critical condition in intensive care in Grenoble.
The car park where the bodies were found is in a quiet, forested area in the foothills of the Alps.
A large number of spent cartridges are said to have been found on the ground around the BMW.
Prosecutor Eric Maillaud told AFP news agency the two women victims were yet to be definitively identified. He said a four-year-old girl was discovered hidden under the bodies around midnight (22:00 GMT). She is thought to have kept still for up to eight hours.
Mr Maillaud said the family was on holiday camping on the edge of Lake Annecy in the Haute-Savoie region, which is a popular tourist destination known for its swimming and water sports.