Murder done by whites against whites, females, and elderly are more likely to be reported by mass media, especially if they used a gun, and most especially if it was an “assault weapon.” By contrast, crimes by or against blacks are barely considered newsworthy. And if you add in mass killing by fire, then deaths by firearms become much less significant.
This and more in a fascinating review by Active Response Training of Mass Murder in the United States: A History.
The bottom line is that the news media seriously distorts the reporting of mass murders. If you were only to look at reported mass murders in the media, you would think that all of them were committed with firearms, in public places, by white offenders who were strangers to their victims. That is a very inaccurate representation of reality.
My advice is that you unplug your television and cancel your newspaper subscriptions. If we know that these sources misrepresent statistics about violent crime, what makes you think that all the other information they report is accurate?