This country does have a problem with portions of the police departments being overly aggressive and violent but it is not limited to African Americans.
http://www.nber.org/papers/w22399.pdf
Fryer’s study is based off detailed police reports from ten major police departments in Texas, Florida, and California. He and his student researchers examined 1,332 shootings between 2000 and 2015, and attempted to isolate race as a variable. Which is to say, they sorted police shootings by context — i.e. “at the scene of robbery,” “at night,” “after being attacked by suspect,” etc. … — and looked at whether cops were quicker to fire at black civilians, when controlling for those contexts.
Fryer calls the results of this inquiry the “most surprising” of his career: The study found no significant evidence of racial bias when controlling for context,
and showed that officers were actually more likely to shoot suspects who hadn’t attacked them when those suspects were white.