A three-year-old boy has died after becoming trapped in a family car in Saint-Gratien, northwest of Paris, during a record heatwave that is affecting much of France and parts of Europe.Prosecutor Guirec Le Bras says the child entered the parked vehicle while his father believed he was napping and became locked by a child safety mechanism for at least 45 minutes before parents found him unconscious; emergency crews could not revive him and his mother is hospitalized in shock.This is the third child vehicle death during the heatwave after two siblings aged two and four were found dead in Carpentras earlier this week; the extreme temperatures have driven three nuclear reactors offline, increased drowning fatalities and strained emergency services across the region.Authorities have opened a manslaughter inquiry to determine whether criminal negligence played a role and health officials are urging households to take precautions for children and vulnerable people while cities restrict outdoor work and close schools.