>> it was the fbi. they were serious. >> twitter, instagram, facebook. you just see things. ridiculously out of control. a click >> a clique of mean girls. were they mean enough to kill? >> it was such a shocking and scandalous kind of case. >> this was diabolical. >> evil comes in all shapes and sizes. hello and welcome to "dateline". for skylar's parent, their daughter what all they could have hoped for. friends and happy at her job. their world turned upside down when their only child seemed to vanish without a trace. at first police thought she ran