What am I trying to justify. Race may play a part in pre-existing prejudices but I don't see ant evidence that the actual shooting was motivated by the race of the victim. Whether or not the cop gets properly punished for this crime is another matter entirely.
Even if the people who called this in did so because they were scared by black kids, that has nothing to do with the motivation to shoot at a moving vehicle. Even if the officer shot because he was afraid there was black people driving, that's not something you can prove, and the only thing that would result from pursuing hate crime charges would be an acquittal.