This affair came to light when harassing and threatening email from Paula Broadwell to another women, whom she thought was a potential rival for Petraeus, was found. The content of the email was "I know what you did," "back off" and "stay away from my guy."
The other women was identified as 37-year-old Jill Kelley, a "social liaison" to a Florida air force base. She had a longstanding relationship with Petraeus. She felt very unsecure after looking at the mail and approached FBI for protection.
James Clapper, Obama's director of national intelligence was informed about this case on Tuesday evening. He discussed the thing with Petraeus on Wednesday and suggested him to resign. And all this issue was not told to Obama until Thursday.
Now, John Brennan can be the possible replacement for David Petraeus. John Brennan is the White House counter-terrorism adviser; he has played an instrumental role in Obama's 'controversial' drone war against Al-Qaeda militants.