Carl Girouard was born around 1996 and grew up in Sainte-Thérèse, a suburb on Montreal’s North Shore in Quebec, Canada. Limited details are publicly available about his childhood or family life, but he was known to have struggled with mental health issues prior to his crimes. At age 19, five years before the attack, Girouard had expressed disturbing thoughts to a doctor, including threats to commit acts of mass violence. 

On the night of October 31, 2020, Carl Girouard carried out a deadly mass stabbing in the historic Old Quebec district of Quebec City, Canada. Dressed in a medieval outfit and wielding a Japanese-style katana sword, he began attacking pedestrians in the vicinity of the National Assembly of Quebec, the provincial legislature. The assault began around 10:30 p.m. local time and appeared to be indiscriminate in nature, with Girouard targeting people at random.

Two victims were killed during the rampage: Suzanne Clermont, a 61-year-old hairdresser and mother of two, and François Duchesne, a 56-year-old museum employee and communications director. Five other people sustained injuries of varying severity but survived. The attacks took place in multiple public locations near government buildings and tourist areas, heightening panic among residents and visitors.

Police quickly responded to the incident, and Girouard was apprehended shortly after the attacks concluded. Authorities reported that Girouard was heavily armed and had been "prepared to cause as much damage as possible," based on items discovered in his vehicle, including gas canisters.

He was taken into custody and later charged with two counts of first-degree murder and five counts of attempted murder. The case was fast-tracked through a direct indictment, which allowed the prosecution to bypass a preliminary hearing. Girouard pled not guilty and was ordered to undergo a psychiatric evaluation to determine criminal responsibility. However, the court eventually determined that he was fit to stand trial.

On 18 June 2021, prosecutor François Godin filed a direct indictment against Girouard, sending the case straight to trial without a preliminary hearing. After a trial in May 2022, the jury deliberated for five days before finding Girouard guilty of two counts of first-degree murder and five counts of attempted murder on 20 May 2022.

On 10 June 2022, he was sentenced to life imprisonment, with the possibility of parole after 25 years, the mandatory minimum under Canadian law for first-degree murder.