Both The New York Times and CBS News identify him as Frederick Humphries, a veteran agent at the bureau who investigated the foiled millennium terrorist plot in 1999.

The FBI agent who helped start the investigation that ultimately led to the resignation of CIA Director David Petraeus has been identified as Frederick Humphries, a veteran agent at the bureau who investigated the foiled millennium terrorist plot in 1999.

Humphries was identified by both The New York Times and CBS News.

Here's more from The Times:

"The agent, Frederick W. Humphries II, 47, took the initial complaint from Jill Kelley, the Tampa, Fla., hostess who was socially active in military circles there, about e-mails she found disturbing that accused her of inappropriately flirtatious behavior toward Mr. Petraeus. The subsequent cyberstalking investigation uncovered an extramarital affair between Mr. Petraeus and Paula Broadwell, his biographer, who agents determined had sent the anonymous e-mails. It also ensnared Gen. John R. Allen, who now commands troops in Afghanistan, after the investigation discovered that he had sent 'inappropriate communication' to Ms. Kelley."

The Times report cited two former colleagues describing Humphries as a solid agent "with experience in counterterrorism, conservative political views and a reputation for aggressiveness."

Earlier this week, it emerged that Humphries was barred from taking part in the case because of concerns he was personally involved. He is believed to have sent shirtless photographs to Kelley, though those were reportedly sent before Kelley received Broadwell's emails. Humphries also took his complaints about the lack of progress in the investigation to at least one member of Congress.

The Seattle Times profiled Humphries' role in the foiled millennium terrorist plot. It noted that his knowledge of Quebecois French helped identify Ahmed Ressam, the Algerian al-Qaida member who was convicted of attempting to bomb the Los Angeles airport in 1999.

Here's how the paper described him:

"Humphries, 34, grew up in Steilacoom, Wash., went to high school in Canada and joined the U.S. Army. He climbed steadily through the ranks, but as a captain in military intelligence he feared he was on track to be a career pencil pusher. He decided to go back to school, winning a scholarship to the University of Tampa and studying criminology.

"He spent a summer during college as an intern with the Sheriff's Office in Sangamon County, Ill., where his stepfather was the chief medical examiner. He met FBI agents working on a missing-persons case, and he was hooked."

In case you're as confused about this story as we are, my colleague Mark Memmott composed a handy guide to the dramatis personae in l'affaire Petraeus.

Copyright 2013 NPR. To see more, visit http://www.npr.org/.

Filed in:

• National Security
• U.S.
• News