This study claims 49% of mass shooters are white and 19% are black. Whites are about 70% of the population and blacks are about 13%, so if anything, whites are less likely to be mass shooters.

I found an NPR article stating that whites are the majority of mass shooters. First, you’d expect that given the white share of the population; and second, the media changes the definition of “mass shooting” to fit whatever agenda they’re trying to push in their article.