After what I went through, I hope I never live in a place that has a mass shooting again.
Why don't you want to live where there was a mass shooting if it's in the past?
I am just scared of living in a place where a shooting has happened.
It is normal to want to avoid dangerous areas. You should consider other factors when choosing a place to live, such as other crime rates and whether you'd find a job. It is fine to have firm criteria for a place you want to live, though.
It's my only criteria, but I can't find a job in a place that doesn't have mass shootings.
If you have to live somewhere that there has been a mass shooting, try to find an area there that you can still feel safe. Maybe a gated community would help. You could also get counseling to try to deal with the fear.