He filmed the chase "by reflex".
Stéphane was at his home in Erigny (Yvelines) near the town of Conflans-Saint-Honorine when he witnessed the intervention of a police crew.
The police then tried to arrest a man suspected of the savage murder of a history and geography professor at the nearby college of Bois d'Aulnes.
In the video extract of a little over a minute, we hear several times the police officers shouting at a man (invisible in the image) to get "on the ground" before him yelling: "Throw your weapon" . A few seconds later, during the intervention of the police (which cannot be seen in the image) on the suspect, about ten shots are fired. The 18-year-old killer of Chechen origin died on the spot. The anti-terrorist prosecution was seized to shed light on the motivations that guided the assassin.