Minorities are almost automatically treated with more suspicion and less leniency than white citizens. Not only are they more likely to be arrested, defendants of different races also usually receive harsher sentences for offenses. Black defendants are often sentenced to maximum terms, while many white defendants such as Brock Turner get off with little more than a slap on the wrist.
This is just one instance of police immediately assuming that when they see a black man, he is probably the criminal they are looking for. There is another case in Newark where cops pulled guns on a ten year old boy claiming that he looked like an adult suspect they were looking for. The kid and the key that called in the carjacking were presumed guilty by racist officers.
The recent black homeowner who was shot after calling 911 to report a carjacking is just the most recent example of the disparate treatment of minorities by police. Minorities are arrested, incarcerated, or shot at much higher rates than whites. There are also endless examples of white youths avoiding real punishment for crimes. One such example is the University of Indiana student who spent a single day in jail, after being allowed to plead guilty to misdemeanor battery instead of rape. Society must address racism openly, or these disparities will never stop.
The simple answer to this is that, police officers are people, and people in this world aren't always the best. Police officers have been seen in a very negative light over the years and have been accused of racism, hate crimes, and of deliberately singling out minority groups. However, by generalizing an entire people you both make all police officers the villains in the situation and you remove the fact that individuals are who are to blame not an entire group.
It's an unfortunate incident but he got out of his home emotionally unstable to meet with the police with a firearm. With all the incident recently of cops being ambush and executed, the cops are with good reason little bit more on the edge when they see someone angry with a firearm getting closer to them.