After a warm summer day spent swimming in a Saskatchewan river, the five friends piled into the car for the 50-minute ride home.

But as they headed towards the Red Pheasant First Nation in western Canada, a tyre blew out. The group pulled into a nearby farm, hoping to find help, they later told police. A shot was soon fired, killing one of the young men in the vehicle, 22-year-old Colten Boushie.

What exactly happened on that August night is set to be investigated this week in a Saskatchewan court, as jury selection begins in a case that has ignited racial tensions in the Canadian province and laid bare the deep fissures between some indigenous and non-indigenous communities.

A local farmer, Gerard Stanley, was charged with second-degree murder, but the 2016 killing set the province on edge.

“Colten Boushie is the Rodney King of western Canada,” said Mark Kleiner, a former pastor with the Lutheran and Anglican churches in Biggar, a town near the site of the shooting. “It is really a flashpoint.”

Despite the scarcity of details, competing narratives soon emerged. Some argued the farmer would not have shot at the group had they been white. Others described the youths as “trespassers”.

As Boushie’s family grieved the death of a caring young man who had been working towards becoming a firefighter, hate-filled comments flooded social media.

“His only mistake was leaving three witnesses,” wrote one rural councillor who later resigned. Another commenter said: “He should have shot all five and been given a medal.”

Duelling fundraising campaigns soon sprang up. More than C$21,000 was raised to help cover the costs of Boushie’s funeral; others raised about C$14,000 to help Stanley’s wife. “Much of the farming community around us who know this family know they are loving and deserving of some help through a difficult time,” said a fundraising page for Stanley’s family.

First Nations leaders criticised the Royal Canadian Mounted Police for fuelling tensions: in a press release a day after the shooting, the force said three occupants of the car had been taken into custody as part of a related theft investigation and another male was being sought. No charges were ever laid.

“The news release provided just enough prejudicial information for the average reader to draw their own conclusions that the shooting was somehow justified,” said Chief Bobby Cameron of the Federation of Sovereign Indigenous Nations.

While the RCMP later apologised for the news release, many in the province pointed to it as another example of how the justice system fails to treat indigenous people equally.

When police arrived at Boushie’s home to notify his family of his death, they did so in an “extremely insensitive” fashion, said Chris Murphy, the lawyer for the Boushie family. “They surrounded [his mother’s] trailer at the Red Pheasant Nation. And came into her trailer and searched the trailer, the same day that her son died.”

Boushie’s mother so overcome with grief she could barely stand, but family members said they were asked by police if they had been drinking.

The RCMP later cleared its own officers of any misconduct in an internal investigation. Boushie’s family responded with a statement asking: “How are we to trust the RCMP when they treat us like criminals when we are the victims?”

The question of race – in the shooting, the police response, and public perception of the case – will loom large during the trial, said Robert Innes, a professor of indigenous studies at the University of Saskatchewan. The province has a troubled history on the subject, he added, citing Saskatchewan’s past as a hub of Ku Klux Klan activity in the 1920s.

What is different now is Canada’s fledgling efforts to confront its historical mistreatment of the country’s indigenous population, such as the system of residential schools which saw more than 150,000 aboriginal children forcibly removed from their homes and placed in a system rife with physical, mental and sexual abuse.

“Whatever the verdict, there’s going to be a real pushback to it,” said Innes. “For indigenous people there’s going to be: ‘Again, the justice system has failed us.’ For a lot of white people, there’s going to be: ‘See, because of the political correctness of our culture, this is how the justice system is rigged against white people.’ Even though there’s no evidence to substantiate that kind of claim.”

In the months since the shooting, hundreds of protesters have gathered outside the court house during court appearances by Gerard Stanley, who has pleaded not guilty to second-degree murder.

Their anger has been tempered by the Boushie family’s calls for calm. “Colten’s death must have a purpose,” his cousin Jade Tootoosis told protesters last year.

“While his death reveals a deep divide that exists between many within this province, it has also brought us here to this courthouse, where we can come together and ask for a fair trial for everyone involved.”

The family’s response has been critical in tempering the simmering tensions, said Kimberly Jonathan of the Federation of Sovereign Indigenous Nations. “I can’t say enough how that prevented more bloodshed,” she said. “We know that there were people that are willing to come and take up arms and say enough is enough. No more dead children. No more.”

This week’s trial could shatter the calm, she warned

“We’ve lost our kids to the Sixties Scoop [when indigenous children were forcibly removed from their families], we lost our kids to residential schools, we are losing them in the justice system, we’re losing them in the jails and the penitentiaries.

“When we face more loss, we get more anger and hatred towards First Nations and [people] saying it’s your fault. Well, we didn’t get there alone. And we’re not going to get out of the situation alone.”