if the victim has been bludgeoned with lots of stab wounds then that's murder irrelevant of the burglary
It depends, people can take multiple shots to the chest area and still keep coming, especially once the adrenaline kicks in. He might of grabbed a knife and stabbed him once, in the heat of the moment the guy might not realized hes been stabbed, or kept coming for revenge, the the old guy has stabbed him again. When youre possibly fighting for your life you arent thinking "oh one stab that will deter him" youre thinking "**** hes still coming at me".
I have a scar on my hand where a blade went through from my palm cleanly through the top. I didn't even notice until quite a while after when things calmed down and noticed the blood pouring out, at which point it started to hurt like hell!