The Canadian flag on all federal buildings and establishments in the country, including the Peace Tower in Ottawa, are at half-mast.
On Thursday, staying vigilant and being aware of heightened security were the main messages to Canadians from authorities.
On mobile? Read the tweet here.
"We're ever vigilant on potential threats and ask the community to remain vigilant as well," said Ottawa police Chief Charles Bordeleau. "We're seeking help from the community — if they have any information that leads us to believe that there are potential threats out there, that somebody wants to do harm to our citizens that they call the police service."
After the second death of a soldier within a week on Canadian soil, people in Toronto are already seeing a change in security levels.
"It is important to be vigilant and any unusual activity should be immediately reported to the Toronto Police Service," said Deputy Mayor Norm Kelly.
There was a noticeable increase in police presence on public transit in the wake of the Wednesday shooting, and additional searches at sports games.
"The message really is simple — if you see something, say something," said Brad Ross, Toronto Transit Commission spokesman.
There's a similar reaction in Vancouver, where more police officers and security staff are being stationed at some public buildings and events, and on transit.
"I would expect that you are going to see a heightened presence probably [Wednesday] and [Thursday]," said Transit Police spokeswoman Anne Drennan. "Beyond that depends on the status in Ottawa."
Legislatures up security but don't close
Across Canada, legislatures continue to be on heightened alert, with some reporting that the days of an open and available parliament may change for good.
“There’s a balance between liberty and security,” said Nova Scotia Kings-Hants MP Scott Brison. “This is a game changer, but how can we approach this and maintain the values of openness and accessibility of democracy?”
No legislatures closed despite additional security measures.
"Our belief is that people are using violence to undermine democracy and want us to be silenced. We refuse to be silenced," said Ontario Premier Kathleen Wynne.
Mubin Shaikhhe, former counterterrorism operative for CSIS and the RCMP, told the CBC that with an elevated threat level, Canadians should expect to see stricter security measures in public places.
"It's going to have to be a balance between the openness of our society where we're definitely not going to militarize. That's not going to happen. Certainly there should be more visible security. This is the world we're living in," he said.
Condolences pour in for fallen soldier
Residents of Hamilton added to a growing shrine at a downtown armoury on Thursday for Cirillo, who served with the Argyll and Sutherland Highlanders of Canada regiment. Hamilton Mayor Bob Bratina said people can sign a book of condolences that is being placed today at city hall.
Messages of solidarity have come in from around the country. Cirillo's death generated an outpouring of grief across social media.
On mobile? Read the tweet here.
On Facebook, the "Rest in Peace Cpl. Nathan Cirillo" page has tens of thousands of likes, and its creator is asking that "on Friday, Oct. 24, everyone wear the colour red in support of Nathan as well as to show solidarity for Canada."
Politicians offered their condolences as well.
“On behalf of all Islanders, our thoughts and prayers are with the family of the soldier who was killed while on duty and to all those affected by these tragic events. We want to thank all law enforcement agencies and first responders who continue to risk their lives to ensure our safety," said P.E.I. Premier Robert Ghiz.
Halifax Chronicle Herald cartoonist Bruce MacKinnon is receiving international praise for his editorial cartoon showing the bronze statues from the war memorial in Ottawa leaning down to pick up the body of Cirillo.
Members of Canada’s Muslim community offered condolences, and condemned Wednesday's attack and the one earlier this week that resulted in the death of a solder when he was run over by a car in a St-Jean-sur-Richelieu parking lot.
“The Ahmadiyya Muslim Jama’at Canada categorically and unequivocally condemns terror attacks on the Canadian Parliament and the National War Memorial as well as on the Canadian soldiers in St-Jean-sur-Richelieu, Quebec,” the organization said in a statement released Wednesday. “These acts of terror have no basis in any religion.”
Britain's Queen Elizabeth sent a message to Canadians as well.
"Prince Philip and I were shocked and saddened by the events in Ottawa yesterday. Our thoughts and prayers are with all those affected," she said in a statement.
Veterans, military react
Canada's military will be reviewing security at different military instillations across the country, CBC's Vik Adhopia reported from St. John's, N.L. Some bases have already closed their doors to members of the public without an appointment and stationed armoured guards at entrances.
Soldiers with 17 Wing in Winnipeg, Man., are reeling over Cirillo's death as security has been ramped up at the air force base.
Two uniformed soldiers carrying assault weapons were standing guard at the entrance to the base as they conducted security checks on Thursday.
Veterans interviewed in Montreal were torn over police suggestions that soldiers not wear their uniforms in public, for fear that they could be the target of another attack.
"If he becomes a bullet magnet wearing a uniform, other people are going to get hurt who are not soldiers, so it's a good idea not to wear the uniform," said Roxboro Royal Canadian Legion Service Officer Sidney Wansborough
Fraser Debney, a retired master corporal, disagreed. He said he refused to cower in the face of the attacks this week.
"I am not going to hide, I’m not going to cover myself up.
"It’s been a very emotional day. It’s been two brother-in-arms who have been taken down, and as a former soldier, yes I feel it," said Debney.
In Calgary, a mother whose son died while fighting for militants in Syria says the government must do more about the threat posed by homegrown terrorists in the wake of Wednesday’s attack.
Christianne Boudreau is the mother of Damian Clairmont, who changed his name to Mustafa al-Gharib and died last January while fighting alongside Islamic State of Syria and Iraq (ISIS) insurgents in Syria.
“It is our problem as Canadians and we have to do something for our country to rein it back in,” she said.
Follow our live blog for the latest updates:
On mobile? Follow the live blog here.