There were several common denominators:

young man, often white, antisocial, often bullied... often addicted to video games like Call of Duty, often on drugs like Ritalin (so, ADHD), often with divorced parents... none of this is to lay a guilt trip on parents but there are often signs that there is a problem, if we could help these kids while they are still young enough, maybe it would cut down on the killings?

the problem with banning guns - it doesn't actually seem to work where it's been tried. I recently read a study comparing murders in the UK, Canada and Australia with the US - guns have been severely restricted in those other countries since the 1990s. But murder rates actually went up in those countries, while they decreased in the US. Here is the study: https://www.publicsafety.gc.ca/lbrr/archives/cnmcs-plcng/cn32226-eng.pdf

And in Australia, it's an island - so you don't have the problem Chicago has. People in Chicago go to Indiana and buy guns, so they get around the gun control laws that way. Australia - can't really do that.

If banning guns actually cut down on murder rates, I'd be all for it. But it doesn't actually work. Getting kids plugged into a community that cares about them however, and getting them the mental health they need, if they need it, would probably help?