Why is it racism. Sikhs is a religion, not a race. Maybe the person didn't like that religion, who knows. It was simply a crime. Just as the colorado shooting was just a crime. A lot of this has to do with the media. People don't see the millions of crimes which are prevented by non nazi police citizens who carry sidearms. It's all about perception.
Lets look at all of the thousands of mexican citizens who have been killed by the American government. Remember "Fast and Furious", and previous programs which were orchestrated by the gov. These programs sent many thousands of semi auto rifles and sidearms into mexico. This was done because they knew many of them would show up in crimes and confiscations. Then the government could pounce. Wouldn't you call this domestic terrorism? Why hasn't the media kept these illegal and unconstitutional programs in the forefront of news.