So, one of my old childhood bullies apparently died a while back in a car accident. I don't feel bad about it at all; in fact I don't really feel anything.
Do you not feel badly because they treated you horribly in the past?
This person made my life a living hell in high school. I'm not sorry that I never have to see them again.
Sounds like this person gave you a lot of reasons not to like them.  I think it's fine that you don't feel upset about it at all.  Millions of people die every day and nobody cares about them either!
It doesn't matter if no one cares about them. I shouldn't feel bad about what happened to a person who was mean to me for years.
I mean it's always strange to hear that someone from your past died, but if they really were that awful to you I totally understand you not wanting to mourn them.