When the Duke's procession arrived at Mass, Lampugnani and the two other assassins (Gerolamo Olgiati and Carlo Visconti) stepped before the Duke, Lampugnani going down on one knee. After a brief exchange of words, Lampugnani rose suddenly, stabbing the Duke in the groin and chest.
Upon the Duke's procession arriving at Mass, Lampugnani and his co-conspirators (Gerolamo Olgiati and Carlo Visconti) stepped forward, with Lampugnani kneeling. A brief exchange ensued, after which Lampugnani sprang up, stabbing the Duke in the groin and chest.