It's a sad state of affairs.
On one hand, the majority of police is the enemy of the free citizen. Most people think police are there to protect them, in truth, they are there to defend the government and the wealthy. Their official purpose is to "maintain law and order", not to work for the good of the people.
In America, the police have a license to kill and do what they want to do, as long as they don't hurt someone in the upper class, or one of their own (case and point, Dorner). Regular people get shot, killed, and assaulted by police on a regular basis in America and an officer is almost never convicted of any wrong-doing no matter what they do to a civilian.
The culture of police in America promotes a "shoot first - ask questions later" culture and a definitive policy of shooting to kill, so that they don't have to worry about lawsuits later. Police know if they shoot and kill a person, the chapter is over and there will never be any real investigation.
In an animal-farm esque manner, all people are equal, but police are more equal to others. If the Mike Brown incident was between two civilians, the cop would've almost certainly had been convicted of manslaughter. But because he's a cop, and they are above the law, he had no charges brought up. If the Eric Garner incident was between Eric and another civilian, the killer would've been convicted of murder, no questions asked. Again, it was a cop, so he was above the law.
Why is this culture prevalent? The wealthy want to make sure they are protected from any possible revolt from the lower classes. That's why police have their hands untied and can do practically anything they want. This is done to keep the public in fear. Police are suppose to be feared, even if you are a law abiding citizen.
I live in New York and I'm more afraid of encountering cops than criminals...because cops can do anything they want. The vast majority of cops here in NYC are extremely nasty, treat people with disdain and disrespect, and abuse citizens on a regular basis.
Now, comes the question, was this justified? Of course not. As luck would usually have it, these two cops were probably the "good ones", because it's always the good guys who lose. However, the motive of the killer is perfectly understandable. Regardless of the circumstances, I feel absolutely no sympathy for cops. As a free citizen, they work against my interests, and would not hesitate to kill me if the chance arose.
And I am a law-abiding, non violent citizen, who follows the law...there is no reason I should fear the police.