My brother lives right near there. It is normally a very quiet, nice neighborhood, and this doesn't sound like an "underclass" crime. More likely a couple of bored, thrill-seeking, upper middle class teenagers. I remember a lot of this kind of stuff in the Seventies - it always turned out to be white kids with wealthy (and extremely liberal) parents.
The girl was from Oakland, with a BMW. I know there are some whites living in Oakland but let's be open and frank here, Oakland is primarily an African American community. A white person living in oakland is not likely to be able to afford a BMW (okay, MAYBE in oakland hills), as it is a poor to lower-middle income area. The type of car driven and the city that the girl lives in make this sound a lot like a crack ghetto, rite of passage, hate crime.
I lived near that neighborhood for awhile and saw not just upscale white kids driving expensive cars,, but also downscale young blacks who were clearly spending their own drug profits. As a matter of fact, I was threatened by one young black fellow in a very expensive car when he almost ran me off a crosswalk.
And on another occasion, I was about to leave a shop when a team of jewelry and expensive clothes-bedecked teenage black girls came in and started behaving very threateningly toward the owner, a small Asian woman. One of the black girls had a very very long "coke" fingernail. I stayed around until they left, as I knew for sure that they'd attack the Asian woman if she were alone.
Oakland is right next door, so don't come to the conclusion that wastrel white girls committed this heinous crime. Though of course, that might be the case.