Mass shooters largely reflect the (male) population: https://reason.com/volokh/2021/03/24/mass-shooters-by-race-a...
That said, mass shootings are a small part of all homicide, so they give the wrong impression of overall violent crime and homicide, and I see no justification for ignoring non-mass homicide. But the media love to focus on them to the exclusion of all else.