It depends what you count and how. The vast majority of US shootings in general are gang and drug related.
If you only count school mass (4+ fatalities) shootings in the US and Canada, if I have got this right from Wikipedia, it looks like there have only been 9 in the last 5 years and 2 of those have been trans shooters. So 22%.
But obviously school shootings are rare, and one incident skews the data strongly
I think it's more useful to look widely and see how a mix of aggressive ideology, a sense of persecution, and poor mental health within the trans community may be contributing to a wider pattern of violent crime of all types.