 On Sunday, 26 April 1478, in an incident known as the Pazzi conspiracy, a group headed by Girolamo Riario, Francesco de' Pazzi and Francesco Salviati attacked Lorenzo de' Medici and his brother, the co-ruler Giuliano, in the Duomo of Florence, Santa Maria del Fiore, in an attempt to seize control of the Florentine government.Giuliano de' Medici was assassinated by Francesco de' Pazzi and Bernardo Baroncelli.He was killed by a sword wound to the head and was stabbed 19 times.