~ story ~
No, I don’t vouch for any of this, but I’m inclined to view it as more likely than not.
Two reasons I think it’s valid:
• Mass shooters undoubtedly prefer defenseless targets over well-defended targets.
• It doesn’t become a mass shooting, if the murdering scumbag is taken down quickly enough by weapons at hand.
So, nothing startling, here. I just liked the pie chart’s simple drama; and it supported my biases.