Girl, 14, cuts her brother's girlfriend's throat and tells her 'Have a nice afte

[Das]

Simple, the girl has participated in occult rituals at some point in her life. I believe she is playing out something she had witnessed before, which glued to her memory.

[ObscureBean]

Is this caused by violent films on TV? Violent games? The Internet?
I've thought that many times, some things are wrong with the youth. I had no violent ideas like that when I was that age. I understand Syria and many countries are terrible places to grow up, but Wisconsin isn't one of them.

It's due to pressure build up.
 
Knowledge is the art of restriction.
It is a double-edged sword, all of the great things that are made possible through the use of knowledge come at an untold cost.
True freedom is unavoidably lost with every new rule/law/theory that science proves to be true. This translates into humans feeling cornered/smothered on a very deep level, beyond their very awareness. The more humans advance the less room they have to breathe. Sometimes coping mechanisms snap.

[Tyrantt]

Is this caused by violent films on TV? Violent games? The Internet?
I've thought that many times, some things are wrong with the youth. I had no violent ideas like that when I was that age. I understand Syria and many countries are terrible places to grow up, but Wisconsin isn't one of them.

It's not due to video games, internet, music, etc... I've grown up with my brother and neighbour and as kids, we played MK, thrill kill, twisted metal... alot , and a lot of violent video games. Also, we watched a  lot of violent movies, horrors, action, thrillers... so in all, we played and watched a lot of violence in our childhood, and we were never restricted by our parents and we grew up in 3 perfectly normal humans. My brother and I are on college, our brother from another mother (neighbour we grew up with) went abroad for work. So I don't believe that violence in games, tv and music causes violence irl, maybe it works on stupid people, i dont know...

[Xester]

Not surprising anymore.  This would be the effect of watching too much violence on tv and movies.  They adopt the imagination into reality and influence her behavior that leads her to this crime.  Guidance of their parents is important in this crucial stage of teenagers.  They are becoming violent and dramatic nowadays.  Is she having desire on his brother?  Why would she be jealous on her brother's girlfriend?