MILWAUKEE, Wisconsin (CNN) -- All Nathan Moore says he wanted to do was smoke pot and get drunk with his friends. Killing Rex Baum was never part of the plan that day in 2004. "It all started off as a game," Moore said. The 15-year-old and his friends were taunting the homeless man -- throwing sticks and leaves -- after having a couple of beers with him. No big deal, Moore says, but he's sorry for what came next. It was a mistake, he said, a sudden primal surge that made him and his friends Luis Oyola, 16, and 17-year-old...