Together with Herbert Kappler, the German Gestapo chief in Rome, Caruso organised the massacre in Fosse Ardeatine on 24 March 1944 as revenge for an attack the day before by Italian partisans on a column of German soldiers in Rome. 335 people, many of them belonging to a Communist military resistance group, were shot during the massacre. One of the victims, Maurizio Giglio, had been one of Caruso's own lieutenants, but had been arrested seven days earlier as a secret agent working for the Allies through OSS.