The arsonist rode into the car park at Valence prison in southeast France on an electric scooter after nightfall on April 14.
After looking at the 16 vehicles there, he targeted two, both of them owned by guards on night duty. The intruder, who was masked and hooded, doused them in petrol, set them alight and filmed himself.
He did not seem to be in any hurry, spending 15 minutes at the site. The police, though, were even slower. By the time they arrived he had ridden away.
