Comparatively, you hear a lot more stories about black people (particularly men) who are treated much more roughly and unfairly by police officers than white persons committing the same crime. This absolutely suggests that many, many law enforcement officers are biased against black people, and is something that society happily reinforces. There are too many black people who are shot, injured, or killed by police officers for a crime that a white person would have been quickly forgiven for. It's absurd.
Yes, there are police officers who are racist, who even kill to get the point across. The media covers those stories. But the media does not cover the vast majority of officers who leave their families every morning, knowing they could be injured or killed, to protect their community. Just because a few officers are evil or racist, this does not mean that the majority is, because most officers ARE good people.
The trend of black men being shot and killed by police is a by-product of ubiquitous technology and a sensationalist media. Police kill people - justified or not - every day in the United States. The vast majority of those killed are white, however, the media tends to latch onto stories about black men being shot because it fits a larger narrative. The ubiquity of technology like smartphones also allows for the media to show these encounters on an almost endless loop.
Police officers, by and large, are not racist. Unfortunately, the race card is the one and only card used every time an incident like this happens. Trust me, policemen do not wake up in the morning saying 'I think I will go out and shoot a black man today." The biggest problem is that constantly crying racism dilutes real racism.
The issue is not that of race. While, statistically, more violent crimes are perpetrated by African American males in their early 20's, it is not specifically because of race. Police officers are trained to handle very stressful situations, and their lives are literally on the line at all times. Police officers need to learn how to better handle the stress of such situations.