I have been to a few rallies/vigils/marches lately and all incidences of violence that I have witnessed either in person or through media has been instigated by the police. As far as I know,every documented case where a formerly peaceful crowd turns into chaos has been started with police shooting pepperspray, teargas, or whatever into the crowd.
I find it really hard to not come to the conclusion that the police is desperately trying to set a narrative to justify a history of violence by escalating more violence, but please, someone, restore my faith.
The question they should ask is, why did the party turn from the people who put it into power and become beholden to public employee unions which encompass police, fire, education, if not regular government employees. Easy answer, the support where the money comes from. People decry corporate money in politics but this money is more poisonous because of its out sized influence because of pressure they can put on any politician who tries to stand up to them; just go google stories of these unions protesting in the streets of the homes of politicians making moves against them, they have bought billboards and even homes nearby to put pressure down.
TL,DR : This is all about money. The politicians have been more than willing to turn a blind eye to police malfeasance; if not problems in fire departments and education; because the money is too good and the groups involved have very big influence over the citizenry.