Even assuming that the trans population is 0.1% (which it isnt, its much greater; usually i have seen 1%, but transphobia, lack of information, misinformation, confusion, fear of change etc. influence the number a lot), this would just mean being trans doesnt impact being a shooter or not and people who say otherwise are spreading lies about transgender people and incite fear and hatred, either from being misinformed or from the want to spread disinformation to achieve a goal

Edit: while writing this, 3 other people also commented