White males commit mass shootings at a greater rate than any other demographic in the United States. That is pertinent to point out when discussing mass shootings.
What is the significance of this shooter being transgender? To my knowledge transgender individuals are more likely to die by suicide and be victims of sexual assault than any other demographic. I don't know of any crime statistic showing transgender individuals commit violent crimes at a greater rate than the general population.
Hale was an illustrator and graphic designer who used he/him pronouns, according to a police spokesperson. Police said Hale was transgender and they initially identified him by his birth name and gender. Based on this sentence the shooter was a FtM transgender person.
I find the more interesting demoographic aspects are the age and biological sex of the shooter. 28 is old for a school shooter. To my knowledge, there has not been a school shooter older than 25 until today. From an article: Female mass shooters are exceedingly rare in the United States, according to FBI data. Of 61 active shooter incidents in 2021, 60 were perpetrated by males and only one was carried out by a female.