You'r right that it was a multi-racial riot. But the majority of looters were Hispanic. Unlike the blacks who were trying to burn down as many buildings as they could, they weren't mad about the Rodney King verdict. They just wanted in on a piece of the action. I read that one group of looters rented a car in Bakersfield and drove all the way to LA to loot.
Here are a couple of citations regarding the racial composition of the looters.
According to a Rand Corporation study blacks were not the majority of the rioters or the looters. Whites were prominently among the looters and the rioters, although the vast majority of the rioters and looters were Hispanic. . .
http://www.gibbsmagazine.com/Studies%20needed.htm
At the time, the rest of the country saw it as a black riot, even though the biggest group of people arrested during the disturbances was Hispanic, most of them immigrants picked up by police and National Guard troops for violating curfew or petty looting.
http://www.inthesetimes.com/issue/24/21/gonzalez2421.html
There was also a justice department official who said early on that as much as 80% of the people arrested during the riots were illegal immigrants. (I think that figure was later revised downward).