I would see it as an accident if they both just started roughing up eachother in the heat of the moment. However, Junta was asked to leave by and official, left, and then came back. By doing this, Junta was not acting in the heat of the moment. He went back, probably thinking, "I'll teach that little twerp a thing or two!" He, then became the aggressor, and the self defense cry is just a bunch of bull.
I do not believe that Junta re-entered the arena with the intent to kill, but death was the result of his actions. I do believe that he should be prosecuted to the fullest extent of the law. Yeah, Costin wasn't a great guy (several convictions for violent crimes), but he was a father of four and a person. I feel bad for the kids. One report said that one of his sons climbed into the coffin with Costin at the funeral. Think, if a man with Costin's criminal history was able to obtain custody, what must the kids' mother be like? Poor, poor babies. Junta's got to do time.