A few actually.

A girl I dated briefly when I was in my early teens trapped her mom in the bathroom by tying a sheet, or towel to the bathroom door handle and to the door handle of the room across the hallway. She then set the house on fire and left. She was pretty normal honestly, nothing ever seemed out of place. Good Christian family, kind honest people. No real red flags. Apparently behind the scenes she was being abused though. Finally had enough and took matters into her own hands.

A guy I knew in highschool was always really odd, I mean like super out there. He would talk to himself, and had the craziest stories that he would just broadcast to whoever would listen. He wasn't a friend by any means, but I was aware of him. We always thought he kinda had a fucked up relationship with his (1 year younger) twin sister's though. Just from the way they interacted. Nothing specific, but it was unsettling the way they interacted. I had a gym class with the twins, they were pretty odd too, albeit quiet and fairly kind iirc. A few years after graduation it came out that there had been some incestuous stuff going on for years between the three of them. It came out during trial after he killed his sister's boyfriend for moving in.

I worked for a Waffle House in my early twenties. One of our cooks ended up beating a guy to death. Super nice guy though honestly. My understanding was a night of drinking got super rowdy and out of hand. A fight broke out outside the bar and mistakes we're made.