Getting married and thereafter, divorced.
Two school incidents come to mind, both involving people at school who were friends, and both fairly minor.
I received a black Nike jacket for Christmas at the age of 14 which disappeared off the coat pegs in the classroom. A friend at the time pointed the finger at two friends, but both pointed the finger at one another.
Similarly, when BMX bikes had a revival around the late-90s early noughties, mine was taken from one of the two friends' house above. This time, the finger was pointed at two people at the house that day, who pointed the finger at the friend from the coat robbery. I later spotted a bike resembling it (tyre branding, and different tyres back and front) in Southport a year later chained up and did nothing. Always regretted not waiting just to investigate.
The friend was later expelled from school for an attempted bursar's office robbery having thought it was full of cash and loot. He was apparently caught in the act.
I seen him a few years later at a football game where he was stewarding. He claimed to be a changed person. He later became an actor starring in the arse end of Two Pints of Lager and a Packet of Crisps.
I once caught a teenager in my garage trying to get under my car, I suspect to remove the catalytic converter.