I suggest looking for articles in major US publications starting with NPR's site. There's just too much to cover in a comment.
Just as a synopsis, systemic racism became a more subtle segregation. POC (People or Person of Color) were systematically made to appear more violent and criminal-like over time. Combine that notion with an idealized notion of the police as hero figures and you have a recipe for rationalizing violence against POC.
Mobile phone videos allowed us to see from the victim's perspective just how brutal police have become.
"How it happens that all those mayors and sheriffs are still in the office if police brutality is such a big issue?"
To this point, you need to understand about voting districts and how POC voting power has been diluted and prevented over decades.
Just as a synopsis, systemic racism became a more subtle segregation. POC (People or Person of Color) were systematically made to appear more violent and criminal-like over time. Combine that notion with an idealized notion of the police as hero figures and you have a recipe for rationalizing violence against POC.
Mobile phone videos allowed us to see from the victim's perspective just how brutal police have become.
"How it happens that all those mayors and sheriffs are still in the office if police brutality is such a big issue?"
To this point, you need to understand about voting districts and how POC voting power has been diluted and prevented over decades.