During the German occupation of Rome, which lasted from September 1943 to June 1944, Pappagallo helped soldiers, partisans, allies, Jews and others wanted by the regime. Betrayed by a German spy Gino Crescentini, Pappagallo was arrested on January 29, 1944 by the SS, as part of a campaign against the Roman resistance. Witnesses reported that Pappagallo shared his meals with fellow prisoners who had not received food. Sentenced to death, he was executed on March 24, 1944 at the Ardeatine Caves.