When pope Sixtus IV needed to borrow money and went to Lorenzo de' Medici, he was turned down due to a disagreement over a personal matter. Pope Sixtus IV then turned to the Pazzi family to borrow money, and quickly made one of the Pazzi family members the archbishop of Pisa.
The Pazzi family quickly put together a plan to assassinate Lorenzo as he was leaving church. The plan was widely know, even the pope was reported to have said "I support it, as long as no one is killed." The assassination attempt failed in killing Lorenzo de' Medici, but succeeded in killing his younger brother Giuliano. As retribution, Lorenzo had hundreds of people executed, including a cardinal and the archbishop of Pisa. Lorenzo also moved on to remove any of the last vestiges of democratic government in Florence, replacing all members of council with de' Medici supporters.