Champ de Mars Massacre
Also called: Fusillade du Champ-de-Mars
The National Guard fired on a crowd gathered to sign a petition for the king’s removal, splitting the revolutionaries into constitutional monarchists and republicans.

Pierre Gabriel Berthault / After Jean-Louis Prieur · Public domain · Source
When the Assembly decided after Varennes not to hold the king responsible, the Cordeliers Club and others drew up a petition demanding his removal. On 17 July 1791 thousands gathered at the “Altar of the Fatherland” on the Champ de Mars to sign it. The mayor of Paris, Bailly, declared martial law, and the National Guard under Lafayette fired on a stone-throwing crowd, killing dozens (about fifty is the figure most often given).
The shooting split those who wished to keep a constitutional monarchy (the Feuillants) from those who wanted a republic. Radicals such as Danton and Marat had to hide or flee for a time, and Lafayette and Bailly lost their popular standing.