Mass shootings also involve African American, Korean American, and male and female middle eastern shooters. So in reality it would be necessary to monitor all of those groups.
That's true, but Ilhan Oman isn't worried about the non-whites. But, as terrible as these mass shootings are, they are still so tiny in number compared to the male population, that it's hopeless to identify the potential shooters ahead of time, except maybe in the final minutes or hours before an attempted mass shooting is undertaken.