Petraeus Quits Post; Evidence of Affair Was Found by F.B.I. - nytimes

WASHINGTON — David H. Petraeus, the director of the Central Intelligence Agency and one of America’s most decorated four-star generals, resigned on Friday after an F.B.I. investigation uncovered evidence that he had been involved in an extramarital affair.  - Petraeus Quits Post; Evidence of Affair Was Found by FBI
David H. Petraeus Resignation Letter