I don't no if there was more to that story that made the court to give him a capital punishment but however there is need for self defense especially when your live is as stake but however that doesn't mean you will not face the law because no matter the magnitude of which somebody attacks you and you retaliated to defend yourself and maybe in the cause of that leads to a bad outcome, the law will definitely take the cause because is forbidden to take another persons live but however if truly proven it was a self defense there could be some consideration during the judgement but definitely shouldn't result to death penalty.
I heard of the story also, but i don't think it was all that came out, it might be as real as they broad casted but no matter the offense, as long the defense that resulted to killing wasn't a direct attack, it doesn't worth the penalty. To the judge that gave the sentence, if he be in the same problem as the guilty, won't he have protected himself, even at worst a jail time seems to be much better than a death sentence.
We should already no about how unrealistic news can be at times, the news might have it that the person did it out of self defense but the real truth might be different and the same could also be that it was a truly a self defense and the news says the opposite so in this case it could be that there was no evidence to prove him right because there are some cases one will claim it was a self defense and nobody will listen because there is no how the incident will happen on the house of the deceased and the accused will say it was a self defense because the first question will be what was he doing in the person house to claim it was a self defense.