Well, technically speaking, depending on the exact terms of reference for "mass shooting", white people (... men ... mass shootings by women are rare) are slightly under-represented as mass shooters vs. their proportion of the population.

Are you sure? I looked into this claim last year and it didn't seem to hold up. As far as I can tell, looking at both FBI and wider media stats, each year white individuals (and white males) seem to be the minority of mass shooters. My theory is that people making this claim are confusing the terms "mass shooter" with "school shooter" and the first category is more than 10 times larger than the second category.

Well, that’s the stereotype alright... but statistically it’s inaccurate.

Well, there’s this (which is clearly trying to push an agenda but is apparently accurate): http://mass-shootings.info/

But it depends on your definition. Certainly the big, intentional “I’m going to kill everyone and then kill myself,” style shootings largely seem to be done by white men.

I told my wife the other week someone should really start an organization that brings gang members to shooting ranges. If they could actually hit their targets a lot less innocent people would die. We recently had three children in a week or so get shot in Minneapolis, all just bystanders.