When I first heard of the attack, I assumed they were black, but looking quickly at a photo I thought I saw white arms. The whole thing makes much more sense if they were, indeed, black.
One set of arms that I’ve seen could have been a white person. And there was a white girl riding on back of one bike.
The three that have been arrested so far are either black or mixed race, but definitely not white. And the guy who got run over is either black or mixed race.
On youtube, there is a video of one of their ‘block parties’. (the group is called the Hollywood Stuntz). There were people of all races there, but it was primarily minority.