This is one of those cases where you might feel bad for someone, even see their good side, but at the same time you can't excuse their choices. His circumstances may have been difficult but that doesn't negate the fact he chose to murder someone. Even if his fiancé instigated everything, it doesn't indicate he was threatened, he chose to follow her out of his own bitter feelings and jealousy. The worse thing too is that he acted against someone who was innocent. It wouldn't be right, but I could see a case for being more merciful if say he plotted against those who bullied him, but that clearly isn't the case here. Like BanditHadron said, this was a prison of his own making.