In 1924, the PNF won the election with 65 percent of the votes, yet the United Socialist Party refused to accept such a defeat—especially Deputy Giacomo Matteotti, who on 30 May 1924 in Parliament formally accused the PNF of electoral fraud and reiterated his denunciations of PNF Blackshirt political violence and was publishing "The Fascisti Exposed: A Year of Fascist Domination", a book substantiating his accusations. Consequently, on 24 June 1924, the "Ceka" (ostensibly a party secret police, modelled on the Soviet Cheka) assassinated Matteotti and of the five men arrested, Amerigo Dumini, also known as "Il Sicario del Duce" (The Leader's Assassin), was sentenced to five years' imprisonment, but served only eleven months and was freed under amnesty from King Victor Emmanuel III. Moreover, when the King supported Prime Minister Mussolini the socialists quit Parliament in protest, leaving the Fascists to govern unopposed. In that time, assassination was not yet the "modus operandi" norm and the Italian Fascist "Duce" usually disposed of opponents in the Imperial Roman way: political arrest punished with island banishment.