In the St. Bartholomew's Day massacre followers of the Roman Catholic Church killed up to 30,000 Huguenots (French Protestants) in mob violence. The massacres were carried out on the national day celebrating Bartholomew the Apostle. Pope Gregory XIII sent the leader of the massacres a Golden Rose, and said that the massacres "gave him more pleasure than fifty Battles of Lepanto, and he commissioned Giorgio Vasari to paint frescoes of it in the Vatican". The killings have been called "the worst of the century's religious massacres", and led to the start of the "fourth war" of the French Wars of Religion.