Earlier quoted context omitted.
That stat becomes more useful when you take into account black Americans are roughly 15% of the population.
I am not sure that per-capita is the right metric. I would prefer to look at it by police encounter or by crime or something like that. This is slightly old but has some interesting data on killings by race: https://www.usnews.com/news/articles/2016-09-29/race-and-hom... In these graphs you can see that total number of killings for white on white or black on black is roughly the same despite the 15% number you quoted…
http://www.fbi.gov/about-us/cjis/ucr/leoka/2013/tables/table...