He had lived some time in Spain, and his knowledge of Spanish, together with his swarthy complexion, which earned him the nickname of the Espagnolet, procured him employment as a spy in the wars against Spain.
Having been converted to the Huguenot cause, he determined to kill Francis, Duke of Guise. Pretending to be a deserter, he gained admission to the camp of the Catholic army that was besieging Orléans. In the evening of 18 February 1563, he hid by the side of a road along which he knew the Duke would pass, fired a pistol at him, and fled.
He was captured the next day, and following torture and a trial, he was sentenced to be drawn and quartered. The punishment, carried out on 18 March 1563, was botched; the horses having failed to rend his limbs, swords were used to finish the job.
During his torture, he had made several contradictory statements, some of which implicated Admiral Coligny. Coligny protested emphatically against the accusation, but nevertheless the assassination led to a vendetta between Coligny and Francis's sons, Henry I, Duke of Guise and Louis II, Cardinal of Guise. This vendetta not only prolonged the Wars of Religion but contributed to the attempted assassination of Coligny during the celebrations of the marriage of Henri of Navarre with Margaret of Valois, and therefore to the St. Bartholomew's Day massacre.