Washington wakes up Monday morning dealing with fallout from the resignation of CIA Director General David Petraeus.
Multiple federal officials tell NBC News that the FBI investigation began with a complaint from Jill Kelley of Tampa, who with her husband is close personal friends with David Petraeus and his wife.
Kelley complained that she was receiving anonymous, emails from someone she did not know.
Officials tell NBC News that those e-mails led to the discovery of others between general Petraeus and Paula Broadwell -- that were indicative of an extra-marital affair.
Previously, Broadwell spoke publicly about her access to the general: "I was embedded with general Petraeus in Afghanistan and it was a little confusing for some of the folks there because I'm also a military reservist with a top secret clearance and then some. So a lot of my former peers didn't know how to treat me."
General Petraeus is not under investigation. He has resigned and spoke with his former spokesperson Steven Boylan Saturday: "He said he had an excellent job, exceptional family, had a great relationship with the White House and in his words, he screwed up and he knows it."
Now, NBC News has confirmed Petraeus conducted his own investigation on the ground in Libya.
Congress is beginning hearings into the deadly attack there and may still ask Petraeus to testify:
"There were five attacks during the year, one prior attack on the consulate itself. The question I have, is, you know, why wasn't something done about it?" asked Senator Dianne Feinstein of California on Fox News Sunday.
General Petraeus may have answers... If he testifies... now, as a civilian.