TAMPA, Florida (USA TODAY)-- The first nasty e-mail from an account named "Kelley Patrol" puzzled Tampa socialite Jill Kelley, but the fact the mystery e-mailer seemed to know her comings and goings is what alarmed her, a source close to the Kelleys said Wednesday.

That e-mail had arrived in the inbox of Gen. John Allen, commander of the military forces in Afghanistan, in May. It was unsigned, came from an account he didn't recognize named "Kelley Patrol" and warned him to stay away from Kelley.

It implied that contact with Kelley could "harm his reputation," the source said. The person, who has direct knowledge of the events and has seen some of the e-mails, requested anonymity because of the ongoing FBI investigation.

"It was an e-mail that was offensive," the person said.

Allen forwarded the e-mail to Kelley. Kelley, who shared the e-mail with her husband, Scott Kelley, was concerned that someone knew of her plans, the person said.

That e-mail and subsequent ones triggered a chain of events that led to CIA Director David Petraeus' resignation after admitting an extramarital affair with biographer Paula Broadwell. Also, Allen's nomination to head U.S. European Command and command NATO forces in Europe has been put on hold because of questions about his e-mail exchanges with Kelley.

In early June, the Kelleys, who have a joint e-mail account, received several more anonymous e-mails -- three to five -- the source said, in a similarly accusatory vein. One e-mail questioned why Kelley was spending time with Allen and Petraeus, a retired general who was Allen's predecessor in Afghanistan, the person said. Another asked whether Scott Kelley knew what his wife was doing.

The e-mails again implied that the sender had observed Jill Kelley and knew her plans, the source said.

"Again, the concern is not that someone is saying nasty things about Jill, but that someone is stalking them electronically and physically," the source said.

The concern that someone might be tracking her and the generals and knew of their upcoming trip to Washington prompted Kelley to call an FBI agent she had met more than a year previously at an FBI Citizens Academy. Kelley didn't act until the third e-mail, the source said.

The FBI agent, who has been identified as Frederick Humphries II, told her he considered the matter serious and would look into it. Kelley provided information to the FBI at the end of June.

Several more e-mails arrived at the beginning of July, but they stopped by August, the source said. Also in August, Humphries was removed from the case, the source said.

A second FBI agent contacted Kelley at the end of July or early August to follow up on the investigation, the source said. It was then, that Jill Kelley learned that Broadwell -- Petraeus' biographer and lover -- had authored the e-mails, the source said.

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Broadwell used at least three different e-mail addresses to send the e-mails. Petraeus is referred to specifically in at least one e-mail, the source said.

"The e-mails reflected that the sender knew where people were or where they were going," the source said.

Kelley "didn't know her name" before then, although she did know about the biography, the source said.

"She didn't make the connection," the source said. "Petraeus never told Jill to this day that he was having any sort of relationship."

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