If you are curious, the largest reason you are seeing so much "violent crime" propagated among the media is because that an officer only needs to meet three conditions to use deadly force making it a more common occurrence in the United States. They, as well as much of the uninitiated public and the greater nations outside the country itself, are fond of viewing these situations with hindsight that those involved do not have, entirely different laws and customs, and with the luxury of not being in life and death circumstances. Many claims of racial bias are focusing upon specific incidents instead of broad net categorization and recording as done by many agencies, but even countless of those potentially suspicious incidents fall back upon the officer's perception. 

For reference, the increased amount of firearms in the United States does not directly correlate with increased violent crime; see Palestine and or China knifing sprees for examples of how mass attacks (other than explicit terrorism) are carried out without firearms. There's other factors for crime that are often ignored.

In the United States it is perfectly justified and legal for an officer who believes the perpetrator has the opportunity, capability and intent to injure or kill them (or others) to shoot. It does not matter why or how beyond that, even if it was a situation that ultimately, in hindsight, did not require shooting.

By standards, opportunity means the chance the attacker would have to utilize a weapon of any form - it need not explicitly even be a firearm, it can even be their person. Capability refers to that they have the means to employ that weapon. Lastly, intent is the apparent interest in doing harm. These might seem complicated but they are not. My best example is this hypothetical story below.

[quote]
A man is stopped by a patrol officer for having a tail light out on his truck. The officer checks the vehicle's information and is informed the individual has a previous criminal record. When contacting the individual, the officer notices the man is wearing a large overcoat. While talking, the man becomes increasingly disruptive and verbally non-compliant to the police officer. When directed out of his vehicle, the man instead puts his hands inside the coat rapidly and fumbles with something in it.
[/quote]
In this situation the officer actually has [i]all[/i] the criteria to shoot, but most will hesitate because they want to confirm there is danger rather than assume. They meet the standard of reasonable objectiveness because A): The individual has the opportunity to cause injury or mortal harm by potentially using a weapon in their coat. B): The individual is physically capable of utilizing that weapon (be it a knife, a gun, their fist, etc) in that close of quarters. C): The individual has the intent because they are again defying an order as their previous arrest record mentioned confirms. Furthermore, the action they are undertaking is explicitly hostile. They only need [i]appear[/i] to be armed or attempting to be.

The worst part about this example used is, is that it was a real scenario. You can see a fair number of these shootings on full, unedited cuts on various social media websites. Do not watch the pared down thing - watch these entire situations in their entirety. In nearly all of them you will see just how much the police will delay shooting unless there's a distinct threat, sometimes so much they themselves (or others) wind up injured or dead.

You might ask why the police might shoot as much as they do, why you see in some of them they fire upwards of five or more times or why multiple police officers might shoot. Unlike movies, to which I can confirm, when people are shot they usually do not go down in a single hit; even direct hits to the head can sometimes give a brief reaction before the hostile individual is eliminated. The other issue stems from the fact that while the United States' police are trained far more intensively than they have been prior, unless they're used to being shot at or threatened with a real weapon, adrenaline has the tendency to whiteout any thorough thought process. There's no time to think, just react, so all you have is training and instinct to fall back on.

This is a long response, but I hope it clarifies things a bit in the simplest of terms one can put them in from someone who has a few stakes in the matter and is from there.