When I was little my mother would sing me very sad World War I and II songs and songs about death, tragedy, etc.
Songs about children dying, fathers dying in coal mines, etc.

I can still sing all of songs and have found them on YouTube as well.
I find myself attracted to and comforted by melancholy music more so than any other. Perhaps it stems from these early experiences.

I once read a book about the melancholy songs of the civil war and how it helped the population of that time deal with the collective grief of such a brutal war.

Interesting topic!

Exactly. You are not alone!
I really don't know what a mutual aid group is.
How do I find them?
What are some examples?
How would they help?

As an American, you are statistically more likely to be struck by lightning than randomly shot.
I am 65 years old and have lived in multiple states. Never been shot at, never shot a gun (except in the US Navy), never experienced any gun violence in my personal life.
As a child welfare worker I have experienced a few cases of gun violence in my professional life of nearly 30 years.

The situation of gun violence is extremely serious but also highly dramatized by media leading to the possibility of miscalculating risk.

Be careful and situationally aware is all the advice I can provide.