In view of the comments about the sources of data above, I found this table of murder stats from the FBI which I presume we can trust?

https://ucr.fbi.gov/crime-in-the-u.s...ender_2013.xls

Admittedly this is from 2013 and things may have changed since then, but it seems that the vast majority of whites are killed by whites and the vast majority of blacks are killed by blacks. Please note these data are for murder in general - there is no distinction between mass killings vs "one on one" killings.