What sentence should this person deserve to receive?

My nephew was stabbed in the heart during a one on one fist fight, my nephew got one punch in before this other person produced a very sharp 3" knife and stabbed him 6 times peircing his heart and he died as a result..This other person ran from the scene and was apprehended by the police sometime later..He now defends himself @ trail by says he was gang attacked, all testimony stated the fight was a one on one,this guy was seen with the knife before, and after the fight and stabbing, the knife was found in his pocket upon arrest, DNA evidence shows my nephews blood was on it in 3 seperate places...What do you think?? 2nd degree murder, or voluntary manslaughter??