Frederick Humphries is the FBI agent who first brought the case of David Petraeus' affair to the Bureau, CBS News confirms.
The four-month investigation that uncovered Petraeus' affair with biographer Paul Broadwell, ultimately leading to his resignation as head of the CIA, was sparked when a Tampa woman named Jill Kelley approached Humphries about harassing e-mails she had been getting.
It began in June as a low-level cyber investigation in Florida. Kelley has done fundraising for the U.S. military and Humphries was a friend, although the details of their relationship are unclear. With his help, the agents quickly traced the emails to Broadwell, a former Army intelligence officer and author of "All In: The Education of General David Petraeus."
The FBI investigation uncovered about a half-dozen e-mails from Broadwell to Kelley. While they did not openly name Petraeus, some of them contained information about his travel schedule - details not usually available to the public.
Concerned that someone may have breached Petraeus e-mail, the investigation continued. It took the FBI some time to discover that Broadwell got the information from Petraeus himself and without his knowledge, rather than a breach.
Once the FBI found sexually explicit e-mails between Broadwell and Petraeus, they realized they had stumbled across an extra-marital affair. The relationship occurred while Broadwell was promoting her biography on tour.
No one has been charged in the case.
Humphries has since been reassigned and his status is being reviewed by the FBI.
Sources also tell CBS News that Humphries once sent a shirtless picture of himself to Kelley, but it happened a long time ago, well before the investigation.