KAMLOOPS, B.C. — An unmarked burial ground at the former Kamloops, B.C. residential school set off a reckoning for Canadians about their country's history and relations with Indigenous Peoples, Prime Minister Justin Trudeau said Monday. 

The prime minister made the comments following a memorial gathering in Kamloops to mark one year since the Tk'emlups te Secwepemc Nation announced a war graves expert using ground-penetrating radar detected the remains of up to 215 children at the former school site.

"It was a difficult year for survivors and their families," Trudeau said at an evening news conference. "It was a difficult year for Canadians as well. We have a long path ahead of us for reconciliation."

Trudeau acknowledged his presence at the ceremony created tensions among some people, but others "told me they were glad I was here."

He received a loud, stern reception during his attendance at a daylong memorial held at the nation's PowWow Arbor and attended by hundreds of people.

"This was an opportunity to come together, to talk about moving forward in partnership," Trudeau said. 

Trudeau was followed by a large group of memorial attendees who chanted and pounded drums as he stopped in the stands, talking face-to-face with people and often exchanging hugs with others.

"We have so much more to do," Trudeau was overheard saying to an elderly woman who he spoke with and hugged.

Others did not appear as friendly, chanting, "Canada is all Indian land," and "We don't need your Constitution."

Trudeau told the crowd he hears their concerns.

"This is a moment for us to realize as great as Canada is as a country, we've made some terrible mistakes in the past," he said.

Earlier Monday, Gov. Gen. Mary Simon told the crowd the atrocities, the death, the loss and the silence of residential schools that Indigenous Peoples knew about for so long is now known by all.

“It’s unimaginable that a place of learning was so cruel. It’s inexcusable that people could commit these atrocities or that people could stand silent as they were committed," she said. 

One year ago, the Tk'emlups te Secwepemc First Nation announced that the graves were detected using ground-penetrating radar at the site of the former Kamloops Indian Residential School. 

They are believed to hold the remains of up to 215 children who died at the school, a finding that led to the discovery of hundreds of other similar sites across the country and triggered a national reckoning on Canada's past and present relationship with Indigenous peoples.