I remember during the Rodney King incident, a videotape surfaced showing LAPD officers using force to arrest Mr. King.
Unfortunately, not caught on tape was the high speed pursuit and the events leading up to the arrest, including King resisting arrest and out of control and strung out on PCP and acting very aggressively before he was eventually subdued.
I tend to think that even if that had been seen on the tape, it would not have mattered to the rioters.