The first email Tampa socialite Jill Kelley received from an account named "Kelley Patrol" alarmed her because the author seemed to know about her comings and goings, a source close to the Kelleys told USA Today.
The emails were later traced to Paula Broadwell, the biographer for former CIA director David Petraeus, with whom he was having an extramarital affair.
Petraeus' resignation last week ignited a scandal now involving the former CIA director, Broadwell, Kelley and Gen. John Allen, commander of military forces in Afghanistan.
USA Today reported the emails told Kelley to stay away from Gen. John Allen.
NBC News said the emails warned “Beware of Jill Kelley. She's the kind of person who could ruin you.” A source told the news network there was information in the email that indicated the author knew Kelley and her husband, Scott Kelley, were planning to meet Allen in Washington.
"Again, the concern is not that someone is saying nasty things about Jill, but that someone is stalking them electronically and physically," a source told USA Today.
That concern prompted Kelley to call the FBI, triggering the present day investigation which found among other things, that Kelley and Allen had exchanged tens of thousands of pages of "flirtatious" emails.
Since the scandal broke, Allen's nomination to head US. European Command and command NATO forces in Europe has been put on hold, USA Today wrote.