From the San Francisco Chronicle:
The trouble Thursday boiled down to a racially diverse mob of about 200 people, many bent on destruction no matter what, confronting police after the day's predominantly peaceful demonstrations ended.
Sporadic conflicts were quelled quickly early in the evening, but by late night at least 50 people -- and maybe as many as 100 -- had been arrested as small groups smashed windows, looted businesses and set trash bins on fire.
It's one thing to be angry because you believe that the system isn't fair and that certain lives are more valued than others. It's another to react to those concerns with violence, which is both unacceptable and completely contrary to what the Grant family wanted.
Before people jump to conclusions, however:
Officials said the main instigators appeared to be organized "anarchist" agitators wearing black clothing and hoods. Many of the most aggressive demonstrators smashing the windows of banks and shops were white.
I believe Fred Hampton once accurately described these kinds of people as "Custeristic."