Nahel was shot by police while driving, after police claim he failed to comply with their stop requests.
Police clashed with protesters in the northern city of Lille and in Toulouse in the southwest, and there was also unrest in Amiens, Dijon and the Essonne administrative department.
The family were enjoying a warm evening on Saturday in their garden in the small village of Saint Herbot, near Quimper, when a Dutch neighbor shot at them several times, the prosecutor said.