It’s one of the Internet’s nastiest tales. The story of Luka Magnotta, and the 2019 Netflix series Don’t F**k with Cats, which covered his crimes, remains one of the most disturbing true crime tales in recent memory.

The sensational three-part series, which explores how a band of Internet sleuths came to solve a grotesque series of killings, became the streamer’s most-watched documentaries of that year. Its gut-punch twists churned up a swell of articles, YouTube reaction videos and discussion threads.

Now, it appears to have inspired a real-life murder too. On February 26, Scarlet Blake was sentenced to a minimum term of 24 years in prison for killing Jorge Martin Carreno in Oxford in July 2021. Blake was described by the judge as having “an obsession with harm and death”, choosing Carreno at random as he walked back alone after a night out. His body was found 24 hours after he was reported missing in the River Cherwell.

Scarlet Blake was convicted for the murder of Spanish engineer Jorge Martin Carreno as he walked home from a night out with friends.

Four months before murdering Carreno, Blake lured a cat into a crate, before taking it home and killing it. She live-streamed its torture, skinning and dissection and put it in a blender. Blake told the family pet: “Here we go, my little friend. Oh boy, you smell like sh-t. I can’t wait to put you through the blender.”

During the 20-minute video, the song “True Faith” by New Order can be heard playing in the background. All these details – from the animal torture to the song – replicate key elements of Don’t F**k with Cats. The jury heard that Blake was inspired to carry out the animal torture after watching Don’t F**k with Cats.

Blake was described by the judge as having “an obsession with harm and death.”

In 2010, Magnotta posted a video of himself killing two kittens by suffocating them in a vacuum bag; a follow-up video a few months later showed him feeding one to a python. In both videos, “True Faith” can be heard. The jerky footage was difficult to decode: Magnotta wore a hood over his face, and the small room was nondescript. Nonetheless, a Facebook page was set up to try to catch the “cat killer” who had violated one of the Internet’s primary codes: Don’t f**k with cats. Soon it had thousands of members.

Within hours of the murder, Luka Magnotta uploaded a video titled “1 Lunatic 1 Ice Pick” to bestgore.com, showing a man being stabbed to death and then dismembered.

“At first, I thought: ‘I’ll just watch how this goes down’,” Deanna Thompson, one of the key sleuths interviewed in Don’t F**k with Cats, told me. “But with this case they were being so stupid – they were focusing on the person, and trying to find someone with the same haircut.”

Many outlandish theories were aired and innocent people exposed amidst the dopamine rush of online justice. “The community was useful in that it helped connect us,” Thompson explains. “But by that point there were lots of people [on the page] and people were just posting random profiles they found on Facebook. It was insane. It was insanity.”

This wider group believed they had a suspect: Edward Jordan, an introverted young man who trolled the investigators by posing as the man in the video. The sleuths turned on him, swamping his profile with abuse. Jordan, who had depression, died by suicide soon after. Disgusted by their tactics, Thompson and half a dozen other sleuths formed a breakaway group. Using the same techniques employed to track war crimes – scrutinizing the videos frame-by-frame, conducting reverse image searches, tracing objects in the room – they eventually zeroed in on Magnotta as the possible culprit. It took Thompson 18 months of all-night investigation. She would log off from her day job as an analyst at a Las Vegas casino and vanish into Magnotta’s dark universe.

Deanna Thompson, one of the meticulous Internet sleuths interviewed for the Netflix docuseries.

In May 2018, her quest took an awful turn. Magnotta uploaded another video. It showed him murdering a Chinese student Jun Lin with an ice pick, dismembering his corpse and performing acts of necrophilia. After the killing, Magnotta mailed Lin’s body parts to the headquarters of Canada’s Conservative and Liberal parties and a school. The online sleuths spotted the video a week before law enforcement did. By the time they persuaded the police to take action, Magnotta was on the run.

Thompson, though, had switched between using her personal Facebook profile and a pseudonymous one while she stalked Magnotta. This blunder led Magnotta to her workplace – he knew she was tracking him and posted a video of himself outside the casino to prove it. He uploaded it two weeks before he murdered Lin.

“I was terrified,” Thompson says. “I knew I had to tell my boss because I worked in such close proximity to him. We had to monitor our mail too because we thought he might send something to me. How the hell do you tell your boss they might get a dead puppy in the post?”

Magnotta is currently serving a life sentence.

After a month-long worldwide manhunt, Magnotta was arrested at an Internet cafe in Berlin. When he was finally apprehended, every commercial airline refused to fly him back to Montreal for trial, and the police paid for a Royal Canadian Air Force carrier instead. On April 12, 2013, after a 10-week trial in Montreal, during which Magnotta sat blankly with his arms crossed – crying only once upon hearing evidence and denying all crimes, citing mental illness influenced by his father’s schizophrenia – he was convicted of first-degree murder and given a life sentence. The case was sensationally covered in the international press with the Chinese media, in particular, subjecting Lin’s family to vicious homophobic speculation. (Magnotta had worked as a gay porn star.)

But by the time Don’t F**k with Cats was released, Magnotta had been behind bars for five years. He was largely forgotten; his disturbing videos buried. Did Don’t F**k with Cats dredge them back to the surface, burnishing his ghastly craving for celebrity?

“How the hell do you tell your boss they might get a dead puppy in the post?”

“The documentary was never going to be serial killer porn; this was never just about murder,” its British director Mark Lewis said. “This story is all about Internet culture, about chasing self-esteem online. But what was fascinating to me was that it functioned like a real-life thriller.”

In fact, Lewis argued he struggled to gain access to the sleuths who helped solve Magnotta’s crimes; key to gaining Thompson’s trust, he said, was a promise not to interview Magnotta. However, he did contact Magnotta’s mother, Anna Yourkin. She denied her son’s culpability, believing his line of defense that he was being controlled by a male partner he’d met while working as an escort.

A memorial service for Jun Lin, the 33-year-old Chinese student studying engineering and computer science at Concordia University in Montreal, who was brutally murdered by Magnotta.

“Yourkin had never done an interview before, so we came just at the right time. She was ready to talk,” said Lewis. “She is desperate to find any redeeming quality she can in her son; to believe Luka so that she can somehow deal with the horrific truth of what really happened.”

Yourkin phoned her son twice a day while they were making the documentary, and visited him in prison regularly. But Magnotta refused to see her anymore after she published her story in a book titled My Son, the Killer in 2018.

Don’t F**k with Cats is a rattling watch, though you never see the videos in full. In fact, the closest you come is watching Thompson view them; her face crumples in shock and she folds into tears before asking that the video be stopped. (She has never made it through them completely.) The approach is uncomfortable, shivering with voyeurism.

“Mark told me: ‘The audience has to understand why you gave up 18 months of your life to this case,’” remembers Thompson. “And, you know, it made a lot of sense what he was saying. He was very understanding and compelling, and I agree it needed to be done.”

The case scarred Thompson. After the initial high of seeing Magnotta brought to justice, her mental health crashed. She tells me she saw parallels with her obsession with Magnotta and that of Michelle McNamara, a true crime writer who died of accidental overdose while enmeshed in the search for the “Golden State” serial killer. “[Sleuthing] can take you down a really dark path,” she notes. “You’re investigating someone’s worst day, right? And it takes a toll on you, especially if you don’t have a good support network.”

Lewis, too, was bruised by the making of the program. “It was a fascinating series to work on, but to be honest it was traumatizing to be immersed in that murky world for so long.”

Lewis only watched the videos twice. “But [anyone] who watches them will be traumatized. I’ve never in my career as a filmmaker seen a detective break down in front of the camera like Montreal detective Claudette Hamblin did while talking about that murder video.”

Lin’s parents declined to be interviewed for the series. But his father gave a public statement to the court. “I had come to see remorse, to hear some form of apology,” he said, “and I leave without anything.”

Magnotta is still serving out his sentence. He reportedly married a fellow inmate, Anthony Jolin, in prison in 2017, with his mother serving as witness.

Yet it seems Magnotta’s story – and the documentary that brought his crimes to wider attention – continues to ricochet outwards in dark and unexpected ways. During Blake’s trial, the police were asked to watch Don’t F**k with Cats to help with their investigation.

In his summary remarks, the judge told Blake: “[It] played a part in cementing in your own mind the link between killing a cat and killing a person.”

Alex Diggins is a London-based commissioning editor at The Telegraph’s arts desk