In the late 1990’s, South Africa was caught in a wave of racist attacks against the while communities perpetrated by black people. The man in this picture was a white farmer targeted by one of these racist attacks. Information I got with the picture suggested that the attackers sawed top of the victim’s head off with a hand saw – I find that scenario slightly unlikely, though not impossible.
I think a shotgun blast to the head is more probable, but who knows. Given lack of blood in the bathtub, it can be assumed that the farmer was murdered elsewhere and placed in the tub after his brain was blown off.