4/16: Massive hunt for Boston Marathon bomber

      |More than 24 hours after two deadly bombs went off at the Boston Marathon, police still have no suspect and few clues. And, as Scott Pelley reports, they're asking the public for their help, and their pictures; Also, an 8-year-old was one of the 3 victims that lost their lives during the Boston Marathon attack; And, following the bombing at the Boston Marathon, eight children were taken to Boston Children's Hospital.