The perpetrator, Kimveer Singh Gill, began shooting outside the de Maisonneuve Boulevard entrance to the school, and moved towards the atrium by the cafeteria on the main floor.

At 12:30 p.m. EDT, Gill parked his car on de Maisonneuve Boulevard near the college campus and was seen removing weapons from his trunk by bystanders.

At 1:30 p.m., police officers dragged his body outside the building, covered it with a yellow bag, then continued the evacuation and the search for possible accomplices.

[12] The television network TVA reported that security camera footage from Place Alexis Nihon showed Gill staking out the area as far back as August 10, more than a month before the shootings.

[20] Police found his car, a black Pontiac Sunfire, parked close to the school, and later searched the house where he lived with his mother, seizing a computer and other belongings.

[21] Around midnight on Wednesday, police confirmed to the media that the suspect was Kimveer Gill, a 25-year-old Laval resident, a graduate from Rosemere High School.

[26] The Pepsi Forum entertainment centre, opposite the eastern corner of Dawson, was open when many of the students came running into the premises moments after the shooting began.

The CSU cancelled all remaining Orientation activities, and instead used its venues to temporarily shelter the evacuated Dawson students and provide them with food, water, blankets, and phones to reach other loved ones.

A coordination team was put in place from the CSU, and the DSU used the Sir George Williams campus as a temporary crisis centre and offered counselling (psychologist, psychiatrist) to traumatized students and staff.

A follow-up study conducted by the McGill University Health Centre Research Institute found that 30% of Dawson students at the time of the shooting suffered mental health consequences including post-traumatic stress disorder, major depression, alcohol dependence, and social phobia, a level twice that found in the general population.

Gill briefly received military training from the Canadian Forces Leadership and Recruit School in Saint-Jean-sur-Richelieu, Quebec, from January 17 to February 16, 1999.

Gill was armed with a Beretta Cx4 Storm pistol-caliber carbine,[36] a Glock pistol (reports are conflicting as to whether this was chambered in 9mm or .45 ACP), and a shotgun.

According to TVA's crime reporter Claude Poirier, Gill briefly held a lawyer hostage and demanded that he bring the bag containing the fourth gun and additional ammunition.

The school invited all students to join them on Monday, September 18, 2006, to meet with staff and faculty for information and support, as well as to retrieve belongings that had been left behind.

In addition, one of the victims, 18-year-old Hayder Kadhim, who received two bullet wounds to the head and neck, challenged Prime Minister Stephen Harper to a gun control debate in a public speech on CBC in response to the shooting.

Three days after the event, Wong, who was born and raised in Montreal and is the daughter of Chinese immigrants, wrote a front-page piece titled Get under the desk, in which she drew a link between all three school shootings in Quebec history (the École Polytechnique, the Concordia University and the Dawson College killings) and the nature of Quebec society under its protective language laws.

Quebec Premier Jean Charest called the article a "disgrace", stating that it "betrays an ignorance of Canadian values and a profound misunderstanding of Québec.

"[48] On September 20, 2006, Prime Minister Stephen Harper pronounced it "prejudiced, absurd, irresponsible and without foundation";[49] the same day, the House of Commons of Canada unanimously passed a motion requesting an apology for the column.

[50] Wong's writing followed the comments of Professor Elliott Leyton, a social-anthropologist who is a widely consulted expert on serial homicide.

In 2007, the Canadian Broadcast Standards Council faulted CKNW, a radio station in Vancouver, British Columbia for airing "potentially dangerous information" during the Dawson College shooting.

During the incident, CKNW had simulcast content from its sister stations in Montreal which included students speaking by cellphone from inside the school.

The council said that as a result of modern technology reducing geographic distance as a barrier, CKNW had breached Section 10 (coverage of violent situations) of the broadcast code.

[52] Gill mentioned the song "A Tout le Monde" by the thrash metal band Megadeth on his blog on VampireFreaks.com on the day of the shooting.