Blacks killing whites in south africa?

i just recently read about the killing of the white supremacist by blacks in sa. and i just spoke to my south african friend about it cause i was suprised. and he informed me this has been going on for a awhile. and he said that he wonders why people are suprised this is happening that after the whites had treated the blacks poorly for many years do they expect forgiveness especially if the whites who killed blacks did not suffer any jail time or concequences for their actions. when i told him this was not the case in america that even after african americans where hung and lynched and their churches blown up they didnt even go on an angry anti white rampage. and he told me that they didnt do it simply because white outnumbered them and they wouldnt get away with it. i want to know is this true