Is South Africa Becoming Increasingly Racially Radicalized?

My girlfriend forwarded this disturbing report today in an instance where South African police fired into a crowd of striking workers, killing 18.  Even more disturbing than an instance of police violence on its citizens is that the striking workers were armed with machetes, apparently this strike has already gone violent in some respects.

The fact that workers, in a country that has long had to deal with poverty for much of its citizens, are becoming more vocally radical isn't too unexpected, though not reassuring.  What really bothers me is that I detected the beginnings of what could become unrest that is more race based.

“N.U.M. is working with the white people and getting money. They forgot about the workers"

I don't expect the old wounds of apartheid South Africa to have healed in only twenty years. But the fact that there are protesters wielding machetes and that some of them specifically mention race, well, that might be a harbinger of things to come. Though I certainly hope that it isn't the case.