French police investigating the mysterious shooting deaths of four people in the foothills of the Alps hope autopsies to be performed Friday will provide new clues to the identity of the killer.

Annecy prosecutor Eric Maillaud has opened a judicial investigation for murder and attempted murder in the case, Joelle Robert of the Annecy prosecutor's office told CNN.

She declined to confirm media reports that Maillaud has said he is investigating a potential family feud, among other leads.

A man and two women, all thought to be British nationals, were found dead in a car, two of them shot in the head, on Wednesday in a parking lot in the Haute-Savoie area of eastern France, near Lake Annecy.

The fourth victim, French cyclist Sylvain Mollier, was found with a gunshot to the head in the same parking lot off a forested road.