yeah, was going to say - there have been trans mass shooters, lol

Another notable case:

https://en.wikipedia.org/wiki/Colorado_Springs_nightclub_shooting

Aldrich’s attorneys have said in court documents that their client identifies as non-binary and uses they/them pronouns, preferring to be addressed as Mx. Aldrich. Neighbors allege Aldrich to have made hateful comments towards the LGBT community in the past, including frequent usage of homophobic slurs. Aldrich never mentioned being non-binary prior to the shooting and was referred to with masculine pronouns by family members. Police testified they found rainbow-colored shooting targets in Aldrich’s home. Experts in online extremism have voiced the possibility that Aldrich’s proclaimed self-identification could be disingenuous, while the Center for Countering Digital Hate acknowledges the suspect’s past actions and impact on the LGBT community.

I am personally inclined to agree that the self-identification is likely disingenuous, a stunt for the courtroom (maybe to make it harder to argue he committed hate crimes).