6. The Cat Killer
This is a fascinating case, as the internet acted as both the inspiration and cure for this horrifying crime. Anyone who has seen the Netflix documentary "Don't F**k With Cats" is undoubtedly familiar with the story of Luka Magnotta, but for those in the dark, it goes a little something like this.
A deranged and attention-seeking young man posts a video online named "1 boy 2 kittens", in which he suffocates two baby cats to death. Soon, he's kicked up a massive storm on the internet, with countless people vying for his death. This attention drove him to make more cat-killing videos before eventually murdering a young man named Jun Lin.
This documentary talks to two leading figures in the internet's hunt for him, Deanna Thompson and John Green. These two were leaders of a Facebook group intent on hunting Luka down. They collated massive amounts of information throughout the pages runtime, such as his identity, motive, and current location.
Berlin police eventually arrested Luka, and while the internet didn't necessarily capture him, it's undeniable that the information found on him was a significant pillar in his capture.