He left office on 24 July 1636, but was still identified as the head of the party that supported the presence of French troops in the prince-bishopric as a counterweight to Habsburg influence.

He survived an attempt on his life on 3 November 1636, when a rider fired a shot in his direction that hit and injured his wife, Ida de Cerf.

In April 1637 he accepted an invitation to dine at the house of René de Renesse, 1st Count of Warfusée, who had been living in exile in Liège since the failure of the Conspiracy of Nobles (1632).

At the banquet, after drinking the health of the King of France, La Ruelle was murdered by a party of Spanish soldiers that Warfusée had smuggled into Liège for the purpose.

Warfusée was hanged out of hand by the mob, and they went on the rampage against prominent members of the "Spanish party", few of whom were implicated in the murder.