"racism within police departments is responsible for the killing of black people in the USA" Firstly, if they are mistaken about facts, that doesn't necessaril

"racism within police departments is responsible for the killing of black people in the USA" Firstly, if they are mistaken about facts, that doesn't necessarily make them racist. That just makes them mistaken, and possibly racist depending on the reasons they are mistaken. Secondly, what is the evidence for this? I've read evidence of racism in US police departments against Blacks, but not specifically in the context of police killings.