Correct me if I'm wrong here:

Middle-left: Japanese girl that stabbed boyfriend. I think he lived though. Pretty sure I heard about it on KYM
Middle-right: Fake baroness that scammed the rich
Bottom left: Encouraged chris-chan to do a bunch of fucked up shit

Top-middle: Lindsay Souvannarath, a Columbine-obsessed neo-nazi who planned to shoot up a mall in Halifax, Canada with her internet boyfriend before their plot was discovered. Also a former KnowYourMeme user.

Bottom-middle: Sol Pais, a teenager who committed suicide near Columbine High School shortly before the 20th anniversary of the massacre. She also had an infatuation with Columbine, but there's no real proof that she was going to commit a massacre herself.