WHY DO BLACK AMERICANS FACE THAT CRUELTY?

Hey all! As newspapers and social media tools show, big protests are happening in US. We watch the subjection of "Black" Americans (Afro-Americans?) to police force and beats and even murders. WHY do these happen? What are the roots of the "official" hate against Black people? What do American people here think? Do citizens exercise this "hate act and / speech" in their dailly life, or is this a state policy?? not seen in societal level that much?