I won't comment much on the shooter's possible motivations because I don't like to speculate with so little information. I've seen people blaming exogenous hormones for the shooting, which is possible, although I'm not sure if it is confirmed that she was taking testosterone and, even if she was, there are many potential confounding factors (like whatever unresolved trauma or mental illness she may had, she possibly trying to prove how "manly" she was, TRA's violent rhetoric and irresponsible talks of genocide and suicide, and so on).

On one hand, I don't think you can rule out, without examining it first, the role that her chosen identity may have played. On the other hand, focusing too much on her identity is missing the forest for the trees.

I read Nashville was the 129th mass shooting in the US in 2023 (that is more mass shootings than days in the year so far...) and the 13th in a school setting. This a very American issue that don't happen anywhere else, not at this rate, anyway, pretty likely because there are too many guns in the US. It's quite easy buying and carrying firearms there, even assault riffles, that belong in the military. What for a civilian would need, for instance, an AR-15 living in a country that is not fighting a war in their own soil? Of course, the US is always at war with someone else, but that happens far, far away.

It's far too easy for wannabee shooters to have access to firearms, even ones designed to kill many people in a short time, yet there is little political will to restrict said access. Supposedly because of some sacrosanct right to bear arms, but more likely because regulations kill profits and the American gun lobby is quite powerful.

And for many Americans, guns seem to be answer to everything. I'm not longer shocked that, after a new mass shooting in the US, there are calls for bringing more guns so the "good guys" can fight off the "bad guys" and protect the innocents. But, for what I've hear over the years, apparently plenty of these gunmen, in their twisted logic, see themselves as the "good guys" fighting for a "just cause" and write a whole manifesto justifying their criminal acts. Not unlike American politicians of either party deciding to invade foreign countries or to make "regimen change" abroad pretending that is for a noble cause like "spreading democracy" or "human rights", all with the full approval of MSM; except that American war criminals are respected and never pay for their crimes. And American troops are honored for "serving their country"; even though that usually means ravaging the invaded countries so as to rich Americans can get richer.

Some may object that I'm linking mass shootings with militarism, but when so many Americans regard an AR-15 as a reasonable choice for self defense...

This is how bullets from an AR-15 blow the body apart

Varmints, soldiers and looming threats: See the ads used to sell the AR-15