The anguished brother of a teen who died trying to save two buddies from a tiger attack at the San Francisco Zoo struggled Friday to understand why the survivors ran out on their mortally injured friend. "If he stepped in for you, why did you leave him to die?" asked 17-year-old Carlos Sousa's brother, Leo, 21. He said his family has been looking for answers since the 350-pound tiger got loose on Christmas and mauled Carlos. By all accounts, the youth was killed trying to get the big cat away from brothers Kulbir Dhaliwal, 23, and Amritpal, 19. But Leo...