Toronto police saw alleged killer Luka Rocco Magnotta as a growing danger to society months before the grisly slaying of Chinese student Jun Lin in late May, according to correspondence obtained by CBC's the fifth estate.

Magnotta has been charged with first-degree murder in the killing and dismemberment of the Concordia University student in a case that drew international attention. The Toronto-born man pleaded not guilty. His preliminary hearing is slated to begin in March 2013.

Correspondence between the Toronto police and an online group investigating Magnotta, and later obtained by CBC's the fifth estate, shows that a detective expressed concerns about Magnotta nearly three months before Lin's death in Montreal.

"I want to find this guy more than anyone out there," a Toronto police detective told the online activists in one email dated March 9, 2012. "Trust me, I want to bring him before the courts even if just to get him psychiatric help."

Magnotta was never found or questioned by police, until he was arrested in a Berlin cafe on June 4 following a massive global manhunt.

The fifth estate also obtained exclusive interviews with members of the anonymous online group who were tracking Magnotta in late 2010 and notified authorities in early 2011 — more than a year before Lin's death — about their concerns regarding Magnotta.

The Animal Beta Project, an 11-member group of activists who pursue animal abusers, told the fifth estate and Radio-Canada's investigative program Enquete that they began investigating Magnotta in late 2010 after a video was posted on YouTube of someone killing two kittens by putting them in a sealed bag and sucking the air out with a vacuum.

Though the video was quickly removed, word about it spread and soon a hunt began for the man they dubbed the Vacuum Kitten Killer.

One member of the Animal Beta Project, who goes by the online alias Baudi Moovan, saw a post about the video in her Facebook news feed and was spurred to help try to find the killer. She joined a 4,000-strong Facebook group called "Find the Kitten Vacuumer … For Great Justice."

"I saw somebody with a complete lack of empathy," Moovan told the fifth estate's Mark Kelley about the person in the video. "And I saw somebody who wanted attention immediately."

Cat-and-mouse game

Moovan and the other Animal Beta Project members — who conceal their real names and locations because they are still in pursuit of online animal abusers — came to the conclusion that the kitten killer was Magnotta.

Jun Lin was a computer engineering student studying at Montreal's Concordia University when he was killed in late May. (Facebook/Canadian Press)

The group believes that Magnotta himself tipped off the online group by planting comments on message boards that he knew they frequented using a variety of online aliases or "sockpuppet" accounts.

"To him, this was a game," another Animal Beta Project member, who goes by the online alias John Green, told the fifth estate.

"When he initially posted the videos of the kittens in the vacuum bag, the YouTube profile name had ‘liked’ a video which was the opening credits to the [movie] Catch Me If You Can, which is about a person who is running away from the authorities," said Green. "And so to us, this was a cat-and-mouse game with him."

Green, Moovan and their colleagues began delving into the online trail left by Magnotta. The group was stunned to find dozens of profiles on Facebook, Myspace and Twitter, plus scores of blogs by the alleged killer painting himself as an international playboy escort and porn star. A vast number of aliases were used by Magnotta to act solely as online "fans" of Magnotta, the group says.

In seemingly desperate attempts to achieve fame and recognition, Magnotta auditioned for two reality TV shows, appeared on Naked News and was profiled in the gay bi-weekly Fab magazine. Magnotta had a clear fascination with serial killers, creating rumours he was dating Karla Homolka and then denying them.

Numerous posts appeared in online magazines and diaries about his dysfunctional childhood and struggles with mental illness.

Photo IDs location

The online sleuths suspect Magnotta joined the Facebook group "For Great Justice" under an alias, keeping an eye on the group as members tried to track him down.

The group scrutinized thousands of pictures Magnotta had uploaded to the web.

In early 2011, members of the Animal Beta Project believed they had finally caught a break with a photograph that showed Magnotta holding a cup of coffee inside a shop.

Because the cellphone picture was stamped with GPS locator data, the group was able to identify the location as Toronto's Eaton Centre and the date as Oct. 31, 2010, about a month before the kitten killing video was uploaded to YouTube.

Armed with reams of information about Magnotta and the latest find, the group contacted the Ontario Society for the Prevention of Cruelty to Animals (OSPCA), which reached out to the Toronto police.

In February 2011, Toronto police opened a file on Magnotta.

Though initially glad their concerns were taken seriously, the online sleuths quickly became frustrated when authorities seemed unable to find Magnotta.

"In our minds, why is it so difficult to find this person?" asked Moovan. "All they have to do is go to their system, type in the name and find them. It boggled us at times."

Authorities contacted again

Then, in late 2011, the kitten killer struck again, posting two new videos: one that showed a person feeding a live kitten to a python and another of a kitten duct-taped to a broom handle and drowned in a bathtub.

Details in this photo helped Animal Beta Project members track Magnotta to Montreal. (Flickr)

The new videos provoked a crisis of conscience among the online group investigating Magnotta.

"When the second set of videos came out again and I turned it on and I watched it, the first thing that came to my mind was 'Catch me if you can.' He was taunting us personally with these videos," says Moovan.

By early 2012, the online investigators had been tracking Magnotta for over a year and had become convinced he would move onto something much worse than killing kittens.

"We were having a conversation with what we believe was a Luka sockpuppet account on a website where videos are hosted," said Moovan. "He said, 'You guys better back off, this guy can snap on a dime and start killing humans.' "

By this spring, the online sleuths had honed their skills in tracking Magnotta down.

Using a recent photo that showed Magnotta posing outside near concrete steps below some distinct street lights, and acting on a tip that Magnotta was in Montreal, the investigators meticulously sifted through Google Street View images of the city's intersections.

The group managed to find the matching intersection in southwest Montreal.

The sleuths again contacted Montreal SPCA and police, pleading with them to act.

CBC News has also learned that the Toronto detective investigating Magnotta warned Montreal police about him months before his arrest in the Lin case.

"I still have the email I sent Montreal PD [police department] stating that yes he was only killing cats right now but that the next would be a human," the detective wrote in an email obtained by the fifth estate.

'Bigger' problem needs change

But in mid-May, someone on the web began promoting and asking questions about a new video called "1 lunatic 1 icepick." There's no evidence the video actually existed at that time.

Watch the fifth estate's documentary, Hunting Magnotta, on Friday. It airs on CBC TV at 9 p.m. (9:30 in Newfoundland and Labrador).

By May 25, a video with that title appeared on an online gore site. Days later, packages containing a foot and hand arrived at the Conservative and Liberal parties' headquarters in Ottawa. Other body parts later arrived at Vancouver schools and were discovered in Montreal.

Moovan recalled her reaction to the discovery that the online video depicting the murder of Lin was real.

"When I came to the realization it was real, I was utterly devastated," she says.

An international manhunt for Magnotta led police on June 4 to an internet café in Berlin.

Members of the online group wonder if they could've done more to alert authorities, but they also worry about the future.

"When you look at the whole picture of what Luka had done, it's not just that he sucked the air out of a bag, he played with people, he manipulated his image, he was terrorizing people and he was killing defenceless creatures," says Moovan.

"It’s not just some person on the internet calling the police and saying, 'Somebody killed a cat.' There's a bigger picture here that I don’t think the system itself takes into consideration here and that needs to be changed."

Watch the fifth estate documentary, Hunting Magnotta, Friday. It airs on CBC-TV at 9 p.m. (9:30 in Newfoundland and Labrador).