The mother of the man identified as the Ottawa gunman has said she is crying for the victims of the shooting, not her son.
In tearful telephone call, Susan Bibeau told AP she did not know what to say to those hurt in the attack carried out by her son Michael Zehaf-Bibeau.
"Can you ever explain something like this?" she said. "We are sorry."
Footage has also emerged showing Kevin Vickers walking through Canada's parliament after shooting Zehaf-Bibeau.
The sergeant-at-arms has been hailed as a hero for stopping the attacker - who had killed a soldier at Ottawa's war memorial - as he tried to storm the country's House of Commons.
Earlier, Prime Minister Stephen Harper said Canada will "never be intimidated" by terrorists who seek to bring "savagery" to the country's shores,
Speaking after the attack in Ottawa, Mr Harper said terrorists would find "no safe haven" in Canada.
"Let there be no misunderstanding - we will not be intimidated. Canada will never be intimidated," Mr Harper said.
"In fact, this will lead us to strengthen our resolve and redouble our efforts - and those of our national security agencies - to take all necessary steps to identify and counter threats and keep Canada safe here at home."
Canada will work with its allies to "fight against the terrorist organisations who brutalise those in other countries with the hope of bringing their savagery to our shores", he added.
Corporal Nathan Cirillo was guarding the National War Memorial when he was shot at point-blank range at around 10am local time on Wednesday.
Witnesses say the gunman raised his arms in triumph after the shooting, which led to a lockdown in downtown Ottawa, lasting until Wednesday night.
The attacker was identified by Canadian media as Zehaf-Bibeau, 32, who US agencies have been advised is a Canadian convert to Islam.
After firing upon Cpl Cirillo, the gunman entered Canada's nearby parliament building where he was pursued by law enforcement officers.
People fled the building, took cover, or barricaded doors as police cordoned off the streets outside.
Officials confirmed 58-year-old Mr Vickers shot the attacker dead outside the MPs' caucus rooms.
At least three people were treated in hospital for minor injuries.
The shooting occurred two days after an Islamic convert ran down two Canadian soldiers near Montreal, killing one of them.
Mr Harper said the two terrorist attacks "are a grim reminder that Canada is not immune to the types of terror attacks we have seen elsewhere around the world".
US President Barack Obama has condemned the shootings, describing them as "outrageous".
"We have to remain vigilant," Mr Obama said.
"It's very important, I think, for us to recognise that when it comes to dealing with terrorist activity, that Canada and the United States (have) to be entirely in sync."
David Cameron responded to the attack on Twitter, saying: "I'm appalled by today's attack in Ottawa.
"I offer my full support to @pmharper and the Canadian people as they deal with this incident."