As you probably know, a Cuban-American self-appointed vigilante, George Zimmerman, shot and killed an African-American teenager, Trayvon Martin, in Florida with everything pointing to racist murder, as the boy was unarmed, had not done anything at all and Zimmerman was almost twice his age. The "fault" of Martin was to be black, young and proud, not feeling intimidated by the self-appointed racist paranoid and criminal arrogance of Zimmerman.
As Trayvon is dead, we only have Zimmerman's account but who can believe a paranoid racist self-appointed street vigilante who had been advised by police to mind his business and go home? Apparently a Florida popular court.
This evidences that Zimmerman's madness is not only his own but is a social pandemic: Florida and probably much of US society seems to believe that Black people can be murdered "preventively" or just because. More or less what Nazis felt about Jews.
It is in many aspects a Klu Klux Klan society, where the privileged segments of society: WASPs and assimilated (including fascist-mafioso Cuban-Americans but surely not most other Hispanics) can go on murderous rampage against the marginated ethnicities, such as African-Americans or Mexican immigrants.
But society is reacting. Thousands have demonstrated in many North American cities against the deeply rooted racist criminal impunity that this sentence consecrates.
While protests were initially peaceful, police has been aggressive and arrested at least 19 people in Los Angeles and New York for "failure to disperse" or "disorderly conduct", in other words: for exerting their right to protest.
A result is that some protests are going slightly violent. In Oakland protesters burned US flags, broke windows, painted graffiti and thrashed a police car.
A 200-strong protest in Miami carried a banner reading: "Don't worry about more riots, worry about more Zimmermans".
Protests have been reported across the whole federation, although the numbers are still relatively low (hundreds, a few thousands at best).