The problem with refusing point blank to acknowledge the relevance of the gender identity of the shooter is that there are a cohort of males who rather than being treated for mental health issues, are affirmed as the opposite sex without question.
We know that many of these young males DO have mental health issues, we know that some of them feel extremely angry if they are not unconditionally treated as the opposite sex. We know that there are subreddit groups called things like 'transguns' and there have been calls to violence by parts of the trans community.
There have not been adequate studies on the impact of cross sex hormones on mental health or aggression.
We know that people with acknowledged mental health issues are prevented from buying firearms but these males are not.
I am not trying to imply that all males who identify as trans are violent or murderers/ school shooters. But you ignore the background of these males at your peril.
This is not the first trans school shooter.