Video of a black suspected criminal dying as police officers kneed on him, after he told them he couldn't breathe and to not kill him, has turned into a pretext for massive riots all over the US. Trump's position is wild west, force against any rioters, including threats of bullets, etc, in his tweets.
Lots of buildings were burned and there was looting and violence. It's been a few days already of it and it continues. The attacks by the citizens were not targeted at the police department exclusively, so they can't overall be taken seriously as a counterattack. The police station was burned, but so was city hall and a bunch of other buildings.
Protest of course can't be exclusively peaceful, otherwise it will have no force. There has to be threat of serious consequences for the authorized minority who have the roles of making laws and enforcing them. Violence has to be there. The effects of the riots will scare authorities into taking measures to seriously try to prevent violence and killing of this type. However, the main officer was charged with manslaughter, the appropriate charge for the action, and the three others we don't know yet, so you can't say the authority response wasn't appropriate. The people probably fear that the response would be just localized to the officer and wider problems would continue, so aren't satisfied.
One mistake is trying to frame it as a black issue, which is to be expected from people who have never left or assimilated or really even read about other countries and cultures, so think their understanding of racism is right when it's actually ignorant. It also diverts from the real issue which is detachment of the vestment with powers over others from responsibility in terms of consequences appropriate to the higher prerogatives.
China is loving it apparently, talking through it's newspapers that the US government should stand with the protesters like they want China to accommodate HKers. This is partly true, although it's a very complicated issue when you have tons of individuals acting and several differentiable groups, doing all kinds of different actions, some not in keeping with protest. Sorting it out has to be individual by individual. We saw reporters being arrested even after identifying themselves. We saw blacks crowding a police car until it looked pretty scary for whoever was inside and the car made a move, with some trying to jump in front or on the hood as it sped off. We saw a group of blacks surrounding a lone police officer to protect him from harm. We saw police cars on fire. We saw a sheriff taking off his accoutrements in front of a press conference-like group and joining the protests, perhaps as a prelim to running for office in the near future. We saw cities putting in place curfews. We saw a mayor stating in defense of the officers involved that 'if you can say you can't breathe, you can still breathe.'
However, I think it's fair to say that if the US government tried to take away the ability of a city or region to elect it's own leaders and wanted to pick the government themselves, as China is doing in HK, the protests would be a lot more serious. The US government does though not have much it can say in it's defense for allowing legal, police, and incarceration injustice, and should have more fear. While violence is necessary, the best control people have over government is funding and defunding them through paying or not paying taxes. This is difficult to do though for individuals, and could probably only be done effectively as a broad movement, so violence is realistically the alternative.