My wife, who was born and raised into her teens in Joburg, has been adamant from day 1 that regardless of whether or not he did or didn't do it (and we both think he did) that it's absolutely 100% possible he thought he was being home invaded and that his life was genuinely in danger.
Houses in Joburg have internal steel bar security doors to lock yourselves into the bedroom section of your home. People sleep with guns next to their pillows. There are 10 foot fences around homes with spikes and razor wire on top and double security gates where you go through the first one, wait for it to close making sure nobody has tail gated you inside, and then the internal gates open.
So while the rest of the world, who simply don't understand the shitful existence white people have in South Africa, think he's making excuses, really he was probably shitting his pants - literally!