 All four victims were shot with the same weapon, a 7.65 mm semi-automatic gun, suggesting to the authorities a lone killer.On November 27, 2011 in Juvisy-sur-Orge, Nathalie Davids, an employee of the laboratory of thirty-five years, was in the parking of her residence, located at 4 rue Pasteur.Her neighbor found her body and alerted emergency services.