Warning: This article is about suicide and may be distressing for some readers.

Canadian highway killers Kam McLeod and Bryer Schmegelsky died in what appears to be a suicide by gunfire, police have confirmed.

Royal Canadian Mounted Police (RCMP) confirmed the two deceased men found in Manitoba on August 7 were the two teen murderers, reports news.com.au.

"The RCMP can … confirm that the two died in what appears to be suicides by gunfire," police said in a statement.

Lifelong friends Schmegelsky, 18, and McLeod, 19, were found dead in thick scrub near the shoreline of the Nelson River in remote northern Manitoba on August 7 — ending a marathon search that made headlines around the world.

Police said the men had been dead for multiple days before they were found.

"While both individuals were deceased for a number of days before they were found, the exact time and date of their deaths are not known," the statement said.

"However, there are strong indications that they had been alive for a few days since last seen in July and during the extensive search efforts in the Gillam area."

Police also confirmed two guns were located with the men and forensic analysis was now under way to confirm that those weapons were connected with the homicide investigations.

Investigators will now assess all items found in Manitoba, where the pair ditched and torched a car before vanishing into the wilderness, along with the previous findings related to the three homicide investigations, in order to get more clarity into what happened to the three victims.

While on the run, the pair was charged with the second degree murder of university professor Leonard Dyck, 64, and named prime suspects in the killings of Australian backpacker Lucas Fowler, 23, and his American girlfriend Chynna Deese, 24.

Mr Fowler and Ms Deese were found shot to death on July 15 after their campervan broke down on the Alaska Highway near Liard Hot Springs.

Four days later, Mr Dyck's body was found 500km away on Highway 37, south of the Stikine River Bridge. A burnt out Dodge believed to have been driven by McLeod and Schmegelsky was found two km away but the childhood mates were nowhere to be found.

RCMP initially failed to connect the three crime scenes, treating the teens as missing persons.

On July 23, police dropped a bombshell, charging them with Mr Dyck's death in absentia and officially linking them to the murders of Mr Fowler and Ms Deese.

By that time, Schmegelsky and McLeod were long gone, having driven more than 4000km in a stolen Toyota Rav4 to rural northern Manitoba, where they torched the car at Fox Lake Cree nation reserve near Gillam before vanishing.

With the world watching, RCMP threw all available resources at finding the pair, sending SWAT teams in heavily armoured trucks, a military jet, drones, sniffer dogs and hundreds of officers to scour more than 11,000 sqkm of heavily forested, swampy and sometimes treacherous terrain.

Gillam and the nearby town of York Landing — which have a collective population of less than 2000 — were placed in lockdown for days as police conducted door-to-door searches of homes and abandoned buildings.

Police were scaling down their search when they lucked out with not one but two breakthroughs on Friday, August 2.

The first was the discovery of a damaged aluminium boat, spotted during an aerial search, near the shoreline of the Nelson River. Around the same time, local tour operator Clint Sawchuk called in what he thought was a sleeping bag on the river bank.

That led to the discovery of several items police were able to "directly link" to Schmegelsky and McLeod on the riverbank — just eight km from where they ditched their getaway car.

Their bodies were found on August 7 in dense scrub, around a km from where the mystery items were recovered.

Sgt Manaigre, who took part in the manhunt, said a group of officers from RCMP Manitoba will remain in Gillam indefinitely looking for clues to assist homicide investigators in British Columbia.

"We were describing (the search) over the last couple of weeks as being some pretty dense bush and some pretty remarkable terrain — in my opinion that's almost an understatement," he told a news conference.

"It was incredible. The steep hills, you've got a fast moving river with very little riverbank. It's unimaginable how … you could traverse that type of area."

Sgt Manaigre said police still have no idea why Ms Deese, Mr Fowler and Mr Dyck were killed.

"That's going to be the biggest puzzle to solve in this investigation," he said. "And we hope we can get some answers on that question."

'I MAY NEVER KNOW WHY SHE WAS KILLED'

Ms Deese's grieving brother, British, said he would remember his sister and her partner as "very loving people".

"I will remember her as an adventurer. I was originally the adventurer in the family, and then she took after me, but she was more adventurous than I was," he told the Today show this morning. "I will remember her as just a very loving person. Her and Lucas were very similar people. They were perfectly matched for each other, and they were very nice. And sources have said that it was Lucas' first girlfriend, and I've really believed Lucas was Chynna's first true long-term boyfriend. So, they were kind of just perfect for each other and both very nice."

Mr Deese said the grieving family "may never truly know why" his sister was killed. "It's discomforting, because anybody — even some of the worst people in the world — if they met Chyna and Lucas, the last thing they would want to do is kill them. It's just hard to accept that such good people can be killed for whatever reason."

Asked whether the apology from Bryer Schmegelsky, the killer's father, was welcomed by Ms Deese's family, he suggested the man was partly in it for the spotlight.

"We have mercy that he raised a son that potentially killed Chynna and Lucas, and Leonard Dyck. But he seems to be going for a little bit of fame and stuff like that."

"I mean, he is getting things off his chest by writing a book and going on 60 Minutes, so that's good," he added. "I don't have anything against him. People's kids can turn out any way, and sometimes there is nothing you can do about the kids you raise. Sometimes they are going to turn out bad no matter what. You can't always blame the parents."