I don't think you can point to any instance where stuff went wrong. I think that there's something that sparks these things to happen, but these things have existed for longer periods of time.
My "worst hobby", as I call it, is analyzing serial murders and what happened in their life that leads to their actions. You name them, Dahmer, Bundy, Manson or Ramirez - every single one of them was raised in very poor conditions with physical and mental abuse, sometimes even sexual or the exposure to these things led them towards a path where antisocial and violent behavior became apparent very early on. And these things happened a lot in poor areas, because poverty is fuel for criminal activity.
And human development is something crazy. The smallest tipping points can cause someone to lose their **** entirely. Mike Tyson has brutal childhood memories and was a model citizen during his time with Cus. The moment Cus died and Tyson losing his familiy surroundings, he became the person he was exposed to as a child.
The root cause for why this **** happens is so ******* deep and horrible, but people don't want to talk about it. They sidestep the issue and go "It's the video games" for example.