The flag-draped casket carrying the body of a Canadian soldier killed in Iraq arrived at an Ontario military base on Tuesday afternoon and began the journey along the "Highway of Heroes" to Toronto.

Sgt. Andrew Joseph Doiron was honoured in a repatriation ceremony at Canadian Forces Base Trenton attended by Gov. Gen. David Johnston, Defence Minister Jason Kenney and other dignitaries.

Dozens of people gathered outside the base to pay their respects.

Hunter Vickers, 19, came from nearby Belleville, saying her family's military background has made her appreciate soldiers' hard work and sacrifice.

"I haven't missed a repatriation ceremony yet and I'm not about to, regardless of the circumstances," she said.

Reg Kirkland, who served in the military for 33 years before retiring, said "it's something we should all come out to if we can."

"I try to make them all," he said.

After the ceremony, a motorcade carrying Doiron's casket headed west to Toronto, where an autopsy will be conducted. That stretch of highway became known as the "Highway of Heroes" during the Canadian mission in Afghanistan.

People began to line the route hours in advance, with some setting up Canadian flags on highway overpasses in the Toronto area even before the ceremony got underway.

In the Senate Tuesday, Senator Carolyn Stewart Olsen of Doiron's home province of New Brunswick paid tribute to him.

"Sgt. Doiron is our first loss in the ongoing mission in Iraq and as such his sacrifice holds special significance in our ongoing fight against terrorism," she said, according to notes sent by her office.

"I would like to thank Sgt. Doiron’s family for giving him to us, to remain forever one of Canada’s immortal sons," she said. "We bring him home in dignity, with all the honour our country can give, and lay him silently to a hero's rest."

Details of incident disputed

Doiron, of Moncton, N.B., is the first Canadian soldier to be killed while serving in Operation IMPACT against ISIS fighters in Iraq.

He was shot and killed in what has been described as a "friendly fire" incident in the darkness of night as his special forces unit was returning to an observation post.

Officials with the Kurdish peshmerga have blamed the Canadians for the shooting, a claim Canadian officials have denied.

Kurdish officials say their forces, allies of Canada in the fight against ISIS, opened fire on the unsuspecting Canadians after they showed up at the front line unannounced.

Canadian officials have said the Canadians were not at fault and had been at the same position earlier in the day and informed the Kurds they would return later that night.

Three Canadians were wounded in the firefight.

One of them was evacuated to Germany while the other two were still in the Iraqi city of Erbil for treatment of more minor injuries.

'Tragic circumstances'

In Tuesday's question period, Opposition Leader Tom Mulcair asked why Kurdish forces weren't aware of the presence of Canadian soldiers on the front line.

Military pallbearers from the Canadian Special Operations Forces Command carry the flag-draped casket of Sgt. Andrew Joseph Doiron at CFB Trenton in Trenton, Ont., on Tuesday. Doiron was killed by 'friendly fire' during operation Impact on March 6, in northern Iraq. (Lars Hagberg/Canadian Press) "These are obviously tragic circumstances," Prime Minister Stephen Harper said, noting that the details were still being investigated. Canadian forces were not expecting to come under fire from anybody, particularly not from their partners, he said.

Mulcair pressed Harper to acknowledge that Doiron had died in combat. He said Canadian soldiers were on the front lines without parliamentary approval, since the Commons had voted in favour of a training mission.

"As we said from the outset, there are risks," the prime minister said. "Thank God [...] we have men and women who go to places like this to confront the risks that exist there so they don't come here."

"We are absolutely following what we said we would do in this Parliament," he said.

Harper told the Commons that yesterday he received a call from the prime minister of Iraq, who expressed condolences and apologized.

Harper said he'd also called Doiron's family to "express our gratitude for his service and our deep condolences for his loss."