Paul O’Neill, a former Treasury secretary who broke with George W. Bush over tax policy and then produced a book critical of the administration, died Saturday in Pittsburgh, according to his son. He was 84. A former head of aluminum giant Alcoa, O’Neill served as Treasury secretary from 2001 to late 2002. He was forced to resign after he objected to a second round of tax cuts because of their impact on deficits. After leaving the administration, O’Neill worked with author Ron Suskind on an explosive book covering his two years in the administration.