Regardug the data on mass shootings: I haven't seen "the data" on this actually. I suspect that a closer look will show that how a mass shooting is defined and how they are reported/recorded is not quite what we think about them in the context of this thread.
Now, as I said, I do not actually know the details, but I speculate that the majority of nom-trans committed mass shootings are gang related, often having to do with drugs. I don't think they are shooting up schools and churches either. I also suspect that the majority of these events involve hand guns rather than long guns.
I don't really know how to do the research to support or invalidate my speculation and would welcome the input of anyone who does.