Canadian police have released dramatic surveillance footage showing the moment a gunman suspected of planning to travel to Syria to fight alongside Islamic militants breached security at parliament after shooting dead a soldier.
The footage emerged Thursday as officials said they had found no evidence of a wider plot following another deadly attack on Monday -- also by a young Canadian convert to Islam who had sought to leave for Syria.
The prospect of more such strikes was at the forefront of many minds in Canada, as a society proud of its reputation for openness and tolerance grappled with a new menace.
Canadian authorities were scrambling to probe the background of the young men, the first of whom ran his car over a soldier, killing him, and another who shot the soldier at a war memorial before storming parliament and being gunned down.
"These are difficult threats to detect," Royal Canadian Mounted Police Commissioner Bob Paulson said. "There is no way of knowing where or when such an attack could take place."
Paulson said the gunman in Wednesday's attack on parliament, identified as 32-year-old Michael Zehaf-Bibeau, had been in Ottawa applying for a passport to travel to war-torn Syria.
It remained unclear whether Zehaf-Bibeau "received any support in the planning of his attack," he added.
His comments came as video surveillance footage showed how the young gunman took less than four minutes to gun down army reservist Corporal Nathan Cirillo and make his way into parliament, where he exchanged fire with police and parliamentary security.
In the House of Commons on Thursday, members applauded Sergeant-at-Arms Kevin Vickers, who fired the shot that stopped Zehaf-Bibeau.
Vickers, a veteran of the Royal Canadian Mountain Police appointed to lead the parliamentary security team and wield the ceremonial mace, has become an inspiration to Canadians struggling to comprehend how two of their countrymen could turn against their homeland.
"The objective of these attacks was to instill fear and panic in our country and to interrupt the business of government," Prime Minister Stephen Harper told the chamber as business resumed.
"Well, members, as I said yesterday, Canadians will not be intimidated. We will be vigilant but we will not run scared."
"We will be prudent but we will not panic and as for the business of government, well, here we are, in our seats, in our chamber in the very heart of our democracy and our work."
Harper then crossed the floor to shake Vickers' hand, and to hug opposition leaders.
Wednesday's attack on parliament came two days after 25-year-old Martin Couture-Rouleau ran over two soldiers in a Quebec parking lot, killing one of them, before being shot dead by police.
Both assailants had sought to travel to Syria where they might join Islamist extremists waging war abroad, officials have said.
Police chief Paulson insisted that Zehaf-Bibeau acted alone and investigators have so far not uncovered any connection between the two attackers.
"Our investigation has not revealed any link between Zehaf-Bibeau and Martin Couture-Rouleau," Paulson told reporters.
Canada has never before been hit by Islamist violence, but it has been threatened in militant broadcasts over its role in US-led air strikes on the Islamic State group in Iraq.
Some Canadians are thought to have traveled to the Middle East to join the group, and others are thought to have developed radical ideas at home, living among Canada's Muslim minority.
Harper on Thursday placed a bouquet of flowers at the war memorial in the Canadian capital to honor Cirillo, an unarmed soldier on ceremonial guard at a war memorial on Parliament Hill in downtown Ottawa.
A large crowd had gathered at the site, still cordoned off with yellow police ribbon, to pay their respects and show their defiance in the face of the threat.
Canada's Muslim community is nervous that the attacks will stir animosity against it, and its leaders were quick to denounce the violence and vow to keep a closer eye on troubled believers.
Imam Sikander Hasni of the Kanata association, who works at the capital's mosque, said he and his colleagues had worked closely with police and had tipped them off to an earlier plot.
"Something needs to be done but at the same time, I think there's a realization that sometimes there is not very much that can be done," he said.