The man who is reported to have shot an assailant on Parliament Hill is a former police officer with a background in providing security services for dignitaries, including members of the Royal Family.
Kevin Vickers, 58, became the sergeant-at-arms in the House of Commons eight years ago after a varied career in security.
He spent 29 years with the RCMP and rose to the rank of chief superintendent, often serving as the face of the national police force in New Brunswick. Before his appointment as sergeant-of-arms, Vickers was director of security operations for the House of Commons.
He had previously worked as aide-de-camp for New Brunswick's lieutenant-governor.
The sergeant-at-arms is responsible for safeguarding the authority of the House of Commons, as well as the safety and security of the Parliament buildings.
As an RCMP officer, Vickers has been responsible for security services provided for the Queen and Prince Andrew.
On Twitter, MPs credited Vickers with saving their lives.
"MPs and Hill staff owe their safety, even lives, to Sergeant at Arms Kevin Vickers who shot attacker just outside the MPs' caucus rooms," tweeted New Democrat Craig Scott.
Veterans Affairs Minister Julian Fantino tweeted: "I am safe & profoundly grateful to Sgt at Arms Kevin Vickers & our security forces for selfless act of keeping us safe."
Justice Minister Peter MacKay thanked Vickers and security forces on Parliament Hill.
"Thank God for Sgt at Arms Kevin Vickers & our Cdn security forces. True heroes," he tweeted.
Although sergeants-at-arms often operate outside of the public spotlight, the events on Parliament Hill are not the first time they have been instrumental in preventing bloodshed in Canadian history.
When army supply clerk Denis Lortie opened fire in Quebec's national assembly in 1984, the legislature's sergeant-at-arms went into the chamber and tried to calm him.
Rene Jalbert, a retired major in the army, offered Lortie a cigarette and eventually persuaded him to release about a dozen hostages who were cowering in the chamber.
The legislature was minutes away from convening when Lortie entered the building through a side door carrying two submachine guns, and at one point sat in the Speaker's chair firing wildly. He killed three people and wounded 13 others.