Surveillance cameras hang from the rafters of gas stations and convenience stores in the smallest Canadian communities.

They're in place to catch thieves. But mostly, they observe Canadians at life's in-between moments: fuelling a truck, checking a cellphone message, buying a lottery ticket.

Last week, cameras in a pair of northern towns thousands of kilometres apart recorded two chapters of an unfolding mystery: a weary couple's intimate hug in the last hours of their lives and an innocuous purchase by the two blank-faced teens suspected of killing them.

RCMP handed out the images to a public transfixed by tragedy.

People struggled to place themselves inside the heads of two young men suspected of killing three strangers.

But anyone can see themselves in Lucas Fowler, Chynna Deese and Leonard Dyck.

"People are inevitably fascinated and frightened by what they don't understand, and I think it's the mystery and the question of why that people find so compelling," says Western University criminologist Michael Arntfield.

"The fact that these people could be targets — the randomness of it frightens everybody, and people are inevitably galvanized by that."

A bond forged through killing

Fowler and Deese were shot on July 14 or 15 at the side of the Alaska Highway near Liard Hot Springs in northern B.C. Dyck's body was found four days later in a highway pullout near Dease Lake, about 500 kilometres to the west.

WATCH: Lucas Fowler and Chynna Deese hugging on surveillance video at a B.C. gas station days before their death

Surveillance video recorded on July 13, 2019 that has been edited for brevity shows 23-year-old Lucas Fowler and 24-year-old Chynna Deese stopping at a gas station in Fort Nelson, B.C. In total, the pair spent just under 17 minutes at the station; nine of them inside it 1:04

Vehicles were found near both crime scenes: the aging blue GMC van that carried Fowler and Deese through Canada's pristine wilderness and the burning pickup Bryer Schmegelsky and Kam McLeod were supposed to be driving to Whitehorse.

McLeod and Schmegelsky are suspects in the double homicide of Fowler and Deese. They are also charged with second-degree murder in the death of Dyck.

Media from Sydney to London covered the killings. The Washington Post and the New York Times reported as the ensuing investigation saw Schmegelsky and McLeod go from missing persons to suspects.

Arntfield has followed the case along with the rest of the world. But he sees it through the lens of a man deeply schooled in the science and history of crime.

If the allegations against Schmegelsky and McLeod are true, Arntfield says they would find themselves in the company of the rarest of killers: couples who form a bond through killing.

Images of Kam McLeod and Bryer Schmegelsky recorded in northern Saskatchewan a few days after three people were found dead in B.C. McLeod and Schmegelsky are suspects in the double homicide of Fowler and Deese. They are also charged with second-degree murder in the death of Leonard Dyck. (RCMP)

The relationship is not necessarily sexual as most people understand it, but it is intimate.

Arntfield says there have been about 120 similar cases in the U.S. and only three in Canada.

"There's people who kick around all kinds of vague ideas as to why these people do this. They're angry at the world, or their parents divorce," Arntfield says.

"In reality, there is an underlying paraphilia or psychological defect that drives this behaviour."

A 'homicidal bromance'?

The three Canadian "team killer" cases Arntfield points to are some of the country's most notorious crimes:

Dellen Millard and Mark Smich, convicted of the first-degree murders of a complete stranger and a one-time lover.

Paul Bernardo and Karla Homolka, the killers of schoolgirls Leslie Mahaffy and Kristen French.

William and Lila Young, the chiropractor and midwife couple who sold and killed infants at a Nova Scotia maternity home from the 1920s to 1940s in what has become known as the Butterbox Babies case.

"There is some sort of disordered bond or intimacy that gets created through the commission of violence," says Arntfield.

"The thought is that even friends or family members — while it may not be an overt sexual attraction to it, there is a disordered intimacy, in this case some kind of homicidal bromance that gets formed and galvanized with each killing."

Dellen Millard, left, and Mark Smich were convicted of the first-degree murders of a complete stranger and a one-time lover. (Facebook, Instagram)

Each of the other Canadian team killing cases generated its own wave of media interest and speculation. Both the Butterbox Babies story and the Bernardo and Homolka murders have been turned into books and movies.

In the United States, public fascination with pairs of killers dates back easily to 1924 and the kidnapping and murder of a 14-year-old boy by Nathan Freudenthal Leopold and Richard Albert Loeb, in what was then dubbed "The Crime of the Century."

The two plotted to commit the perfect crime over seven months in which they planned every element of the abduction and killing of Bobby Franks in Chicago.

The central question: Why?

In every case one central question inevitably hovers above the tragedies: Why?

The killings in northern B.C. are no exception.

At a public meeting in a small high school gymnasium this week, the head of Dease Lake's four-member RCMP detachment was asked about possible motives by residents who packed the room to hear Sgt. Steve Woodcox provide information on events that had set their world on edge.

Woodcox was unable to answer. Only the people who committed the homicides know for certain, he said. And they may take their secrets to the grave.

Dease Lake RCMP Sgt. Steve Woodcox speaks to residents concerned about three killings in northern B.C. (Jason Proctor/CBC)

Of course that hasn't stopped people from speculating and guessing. Many of the locals standing and sitting at the meeting drove more than 80 kilometres north from the First Nations community of Iskut to attend.

Their journey took them right past the spot where Dyck's body was found. A white tarpaulin still covered the ground. Forensics investigators continued to comb through McLeod and Schmegelsky's truck for evidence.

Band manager Maggie Dennis said speculation about the crime ran rampant among the band's 300 residents since the Friday morning when Dyck's body was found within minutes of the burning truck.

It's human nature, but Dennis feared adults might be scaring their children.

Amateur sleuths, Facebook and Google

The residents of Iskut worried they might have a killer or killers in their midst.

The public searched for explanations back in Leopold and Loeb's day as well. But amateur sleuths can now search the Facebook pages of victims and suspects in the B.C. killings.

The RCMP have credited the public with providing information that helped track the movements of Schmegelsky and McLeod from B.C. to Manitoba. (Ben Nelms/CBC)

They can use Google Maps to trace a possible route from Dease Lake to the remote town of Gillam in Manitoba that would have taken Schmegelsky and McLeod through Saskatchewan's Meadow Lake, where they were caught on camera.

They can email tips to police, discuss theories of crime in online forums and — in some cases — hope their dashcam footage might have caught the accused as they drove past.

RCMP have credited the public for coming up with the evidence that allowed them to track the pair. They've seen tips roll in from across the country and continue to ask the public for any assistance they can offer.

A final gesture of love

We're in an era when true crime dominates streaming services like Netflix and podcast providers like Apple and Spotify. A book about one obsessive woman's search for the Golden State Killer topped the bestseller list.

"I think we should distinguish this, which is an active manhunt that has a serious dimension of serious public safety to it, versus the media firestorm that surrounds any case of serial murder," says Arntfield.

But he says the interest in true crime comes in waves — often prompted by societal conditions and shifts in technology. This time, it's social media.

"There's a dimension of interactivity to it, and I think that's a part of what is buoying the resurgence in true crime," says Arntfield.

"The medium used to deliver these stories now has changed to the point where it's not Geraldo back in the '80s or those old magazine shows. They're ubiquitous and they allow for the conversation to keep going and they allow for people to become hobbyists."

Whether that's a good thing or a bad thing, Arntfield says, is too early to say.

But whenever and wherever it happens, true crime is committed on real people.

And in the drive to comprehend, precise memories of victims can become lost to the overabundance of information about perpetrators.

We'll never understand what exactly lies behind the eyes of Bryer Schmegelsky and Kam McLeod in the images released by RCMP.

But the love between Chynna Deese and Lucas Fowler is as obvious as it is heartbreaking.