This body-parts story is a thoroughly horrible business, but it is somewhat cheering to see how many people worked long and hard — though unsuccessfully — to try to prevent the tragedy from happening.

As soon as a kitten-killing video was posted to YouTube, in December of 2010, people around the world started to work together on websites, sharing information and trying to track down the guy who killed the cats.

By Wednesday, when police announced that Luka Magnotta was the suspect in the body-parts homicide, animal lovers around the world had been on his trail for two years.

They notified humane societies and police departments in Toronto and Montreal, posted rewards, spent countless hours poring over videos and photos for clues, established a thick dossier on Magnotta, and identified fake Internet personas that seemed to be leaving false trails to confuse the people pursuing him.

They were motivated by four horrible videos in which a young man gleefully kills kittens. In the first one, in 2010, a young man alleged to be Magnotta suffocates two kittens in a plastic bag. A few weeks later, he posted a related video.

By January of 2011, after frantic online searching, animal lovers tentatively had identified Magnotta as the suspect. They meticulously compared photos that Magnotta posted of himself, identifying jewelry and furnishings that appeared in both, until they were certain they had found the right guy.

They then focused on finding him, something which was made more difficult by the many apparently fake photos Magnotta seems to have posted — using a host of false online identities — showing him in cities around the world.

Volunteers analyzed the digital fingerprints of the photographs and identified the camera used to make the videos, linking it to photos of Magnotta. They tracked down products in the background of his pictures, tried to figure out when and where they were sold.

They tried to place him in particular places at particular times, using film posters and landmarks in the backgrounds, analyzed accidental reflections of his camera, and established that he was in the Toronto area.

In December 2011, he posted two more videos, in which kittens were killed in horrible ways.

On the Facebook group where they shared photos, member after member fretted that he would move on to human victims.

"He might end up killing human beings one day though," wrote one member in December 2011. "He might just not stop with animals. He needs to be caught ASAP."

They posted images of him around the Internet, and on bulletin boards in the real world.

By January, they thought he was in Montreal.

"Its possible that he has a part time residence in Montreal," one Facebook user wrote. "We have verified the info, but we do not know where exactly in Montreal."

In February, a British national involved in the hunt for Magnotta wrote to a Canadian involved in the animal rights movement, looking for help.

"We are currently searching his current location and have pinpointed two addresses in Montreal," he wrote. "We had one sighting (to be confirmed) as recent as yesterday. The net is closing in. However, animal rights laws in Montreal are almost non-existent.