While under orders to suppress a Royalist counter-revolution, he commanded the execution of 4,000 civilians, mainly priests, women and children in Nantes, some by drowning in the river Loire, which Carrier described as "the National Bathtub.

Carrier worked in a law office in Paris until 1785 when he returned to Aurillac, married, and with the outbreak of the Revolution joined the National Guard and the Jacobin Club.

He established a revolutionary tribunal in Nantes and formed a unit of troops called the Legion of Marat, in order to suppress the revolt of anti-revolutionists and dispose quickly of prisoners in the jails.

[5] In a twenty-page letter to his fellow republicans, Carrier promised not to leave a single counter-revolutionary or monopolist (hoarders or aristocratic land owners) at large in Nantes.

[8] Some alleged that Carrier ordered young male and female prisoners be tied together naked before the drownings, a method which was called a "republican marriage", but this accusation was later found to be a rumor started by counter-revolutionaries.

"[12] After this statement, a fellow representative, Phélippes, vocally charged Carrier with drownings, wholesale executions, demolitions, thefts, pillaging, laying waste to Nantes, famine and disorder, and the butchering of women and children.

Men from the "Marat Company," a militia that Carrier used to purge Nantes, were present during the trial, including Perro-Chaux, Lévêque, Bollogniel, Grandmaison, and Mainguet.