I was at school with a lad who, when we were in our early 20s, came home from a shift at work one day to find his entire large family murdered and his dad was later found hanging in the garage, having killed them all first. I barely remember the rest of his family, maybe a sister - or the dad, but I'd have seen them around a lot as it was a village. When it happened I lived a couple of hundred miles away but saw it on the national evening news...
My ex was done for harrassment (three times - got away with it once as it was a small, Hertfordshire court who were so naive and provincial he managed to totally pull the wool over the magistrates' eyes. He went on to be convicted later in other courts, with proper judges, twice. I often wonder if those magistrates read it in the papers and realised they'd been made idiots of).
My brother had a close friend in childhood, who he lost contact with. Years later, some kind of sinister services police come knocking to ask if he knew where his long lost friend was (He didn't). Apparently he'd joined the navy, done some sort of crime and gone on the run. How they tracked down his childhood friends, I dread to think. We never found out if they caught up with him or not, or precisely what he'd done.
My kids' IT teacher was convicted of having and distributing child pR0n. Worse still, some of the pR0n was about animals. If you'd asked me after any parents' evening who was the nicest and most caring teacher - I'd have said him. He had a wife and a young child and I think they lost their house and everything.
The 'road rage' killer Tracie Andrews' victim was the bus driver on the bus route that went past my house. We used to call him 'the handsome bus driver' and everyone on the route knew him and liked him. Never knew her but it was shocking knowing the victim in a high profile case - the second we saw his picture on the news, we recognised him.