For me, the important part is the "after rationally considering" part.
Tragic as it would be, if it had been a violent argument where he started waving a gun around, I doubt he would be rationally considering very much.
There are many definitions, and that is far removed from the legal one in the UK. Not sure what the SA one is, but they charged him with murder so it must be similar.
There is no rationally considering part in the legal definition here. Intent is what it means, and it is a given that firing a gun towards someone has intent.