Composer Marc Shaiman recalls the devastating moment he learned from Billy Crystal that his longtime collaborator, Rob Reiner, and his wife, Michele Singer Reiner, had been found dead in their home, saying he remains in shock. As he plays music from Reiner's film "The American President," one of the scores he’s most proud of, Shaiman becomes emotional with Tracy Smith, struggling to believe his dear friend is gone: "I just can't believe it." | CBS Sunday Morning