Imprisoned in the Louvre, he was approach by Jacques Clément a Dominican Friar who pretended to be a royalist that desired to cross the siege lines to the king Henri.

[4] Under the command of Jean VI d'Aumont Brienne participated in the re-capture of the ligueur held city of Angers in early 1589.

[5] At this time, Épernon was in internal exile, down south in Angoulême and Brienne represented his patrons interests in the Touraine.

[6] On 28 April 1589, Brienne was leading a small reconnaissance party at the Château de Saint-Ouen near Amboise when he ran into forces under Charles, Duke of Mayenne.

In the skirmish that followed his small party was able to kill 50 ligueurs, but in the chaos he was captured by the ligue army, and he was quickly moved back to Paris as a captive.

[7][5] The ligueur army had learned of his parties position due to information delivered to them by Épinac, the archbishop of Lyon.

Épinac had been a prisoner of the king, but his captor De Gast, an enemy of Épernon and his clique, allowed his escape.

[6] Jacques Clément, a Dominican friar made the fateful decision, with Paris surrounded by the royal siege, to kill the king.