Abroad in well-developed nations with healthy economies, violent police aren't so much a thing. Our police mimic our own American society, which is inherently violent and promotes criminality (through a draconian justice system that has been dolling out harsh penalties for minor crimes for decades, allows white collar crime to thrive, promotes racial injustice through segregationist state laws, removes social support for the vulnerable people who are most likely to become criminals through necessity, etc). And we're surprised that within this framework, the authorities abuse all the latitude we give them. American police aren't uniquely screwed up, they're just American.