In February 1563 Francis, Duke of Guise, was assassinated. While the murderer was seized and immediately put to death, Anna took all possible steps to sue the leader of the French Huguenots, Gaspard de Coligny, whom she held responsible. During the next three years, the widow put pressure on the king and his courts of justice with her petitions, but in January 1566 the king's council declared the admiral of Coligny innocent and imposed eternal silence in the matter. Consequently, most of her contemporaries held the widow of the Duke of Guise responsible for the shot which was fired on Coligny on 22 August 1572 and which became the starting signal for the St. Bartholomew's Day massacre.