First of all, more whites are killed by cops than blacks. More blacks are killed per capita by cops than whites which statistically makes sense because violent crime rates are higher amount blacks than whites. In 2012 according to Bill O'Reilly there were reportedly 123 blacks killed by police and 326 whites killed by police. O' Reilly has been critized on these numbers because 97 of the 326 whites were actually white Hispanics and that the number of deaths by cops may have been under reported.
However, these numbers show that it's not just blacks that are killed by police, but there are many of other races also killed by police. With approximately 800,000 cops performing probably hundreds of millions or perhaps billions of calls each year, these numbers do not seem extraordinary to me. I would like to think that the cops were right in using deadly force most of the time. However, determining what was justified and what was not can often be controversial. It's just my opinion, but I beleive that if the justified deaths by cop could be accurately subtracted from the totals, the percentages of unjustified deaths by cop would be miniscule.