There were a few cases in my life.
First, there was a guy which was in the same class as me on the elementary school and in the same soccer-club (or football, whatever you call it). He died in a car crash a couple of years ago. He was on one of the back-seats.
I can't say that I was really sad because I don't remember much contact, but I felt sorry for him, his family and friends (of which one was the driver who survived).
The next case was a guy that was in a parallel-class of secondary school for a few years. He bullied me a few times and I really hated him. He also was drug-addicted and had some trouble with the police. In the end, he committed suicide.
I had mixed feelings about that. But now, a couple of years after that, I just feel sorry that he couldn't handle his life.
The last, but most emotional case is about a teacher from vocational college (don't know if this is the correct translation).
He was our german-teacher. Nearly all of his students liked him a lot, he was very cool, chill and friendly. He was the prime example of a good teacher.
But he was a smoker and had serious heart problems. A few months after I started vocational college, he had a heart-attack and had to recover for about a year, until he came back. But that didn't last long. He got another heart-attack soon after he came back to work and didn't survive this time. We all were very shocked and felt really sad.
Life is just unfair.
EDIT:
I just remembered another person.
She was also in my parallel-class of secondary school. I didn't really know her, but she was very kind, that's something I do know. She died of cancer as a teen. There was a memorial day in school for her.