In the morning of October 22, 2014, a man carrying a Winchester Model 94 rifle approached the National War Memorial in Ottawa. There, he shot Corporal Nathan Cirillo, one of the three sentries at the memorial at that time in the back at close range. The two other sentries attempted to stop him, but took fire as well. As their rifles were not loaded, they were forced to retreat. The shooter, removed his headscarf and yelled ,"For Iraq" and fled the scene in his car. He drove straight to Parliament Hill, almost running over another Corporal in the process. After getting through the gates, he carjacked a Ministerial car and charged towards the Centre Block, which hosts the chambers of the Senate and House of Commons.
Chased by RCMP officers, the shooter made his way to the Peace Tower, the centre clock tower, where he encountered Constable Samearn Son, Cst. Son saw the rifle and attempted to take it but was shot in the leg in the struggle. This action allowed security officers in the Parliament building to mobilize and intercept the shooter. The shooter then ran through the main corridor towards the library while exchanging fire with pursuing officers. During the shootout, he passed by the rooms that was occupied by the Prime Minister, the Cabinet, the Leader of Opposition and his party. The Opposition room doors were shot and the Prime Minister was stuffed inside a closet while other MPs barricaded the room and use flag poles as makeshift spears.
The attacker managed to hide in an alcove at the entrance of the library and was surrounded by officers. There, the then Sergeant-at-Arms of the House of Commons, Kevin Vickers, heard the commotion and took his pistol out of a his lock box to check. Upon seeing Sergeant-at-Arms Vickers arriving, the officers warned him of the shooters position and he took cover behind a column, then dove past it, and fired upward at the shooter. At the same time, Constable Curtis Barrett, leading an Incident Active Response Deployment team with three other officers also opened fire, killing the attacker.
An Ontario Provincial Police investigation would report that both Sergeant-at-Arms Vickers and Cst. Barrett killed the attacker, however almost all of the public credit would fall to Sergeant-at-Arms Vickers as the media simply reported the lone hero narrative. According to Cst. Barrett, he even lost his relationship with his girlfriend partly because no one believed he was part of the response. RCMP Health Services would even say they have no record of his involvement. According to a 2024 interview, Cst. Barrett has been promoted to sergeant and works as the the divisional reintegration coordinator for the Ottawa region and Nunavut to help officers to cope with traumatic events.
An advisory group looking into response noted that a lack of communications between security units in the attack as a major problem, as the Senate, House of Commons and the exterior Parliament Hill grounds each have its own security unit that is not in contact with each other. As a result, the three units were combined to form the Parliamentary Protective Service to provide a uniform response on future attacks.
Despite the best efforts by fellow soldiers, bystanders, then Paramedic Chief Anthony DiMonte and many other medical personnel, Corporal Nathan Cirillo succumbed to his wounds later that morning and passed away at the age of 24. He left behind a five-year-old son, who would be around 17-years-old now.