Protests erupted in Madison, Wisconsin, last weekend following the police killing of another unarmed black man.
Tony Robinson was shot on Friday of last week by officer Matt Kenny who forced his way into an apartment after saying he received reports of a disturbance. He shot 19 year old Tony who later died in hospital.
No gun or other weapon was found at the scene.
The killing came just days after the Department of Justice (DoJ) said it would not prosecute officer Darren Wilson.
Wilson is the white cop who shot dead unarmed black teenager Michael Brown in Ferguson, Missouri, last year.
A damning DoJ report published last week showed officers in Ferguson target black people for stop and search more frequently and have sent each other racist emails.
Thousands turned out to hear president Obama speak in Selma, Alabama, to commemorate 50 years since civil rights marchers were attacked by police.
But anger was widespread, with people holding signs calling for justice for black deaths.