New details emerged on Sunday about the extramarital affair that abruptly ended the career of CIA chief David Petraeus, including the identity of a second woman whose complaints about harassing emails from the woman with whom he had the relationship, Paula Broadwell, prompted an FBI investigation.

A person familiar with the investigation identified the second woman as Jill Kelley, a long-time friend of the Petraeus family and a Tampa, Florida volunteer social liaison with military families at MacDill Air Force Base.

Kelley went to the FBI after receiving threatening emails that eventually were traced to Broadwell, law enforcement and security officials have said, prompting an investigation that turned up evidence that Petraeus and Broadwell were having an extramarital affair.

"We and our family have been friends with General Petraeus and his family for over five years. We respect his and his family's privacy and want the same for us and our three children," Kelley said in a statement obtained by ABC News.

Broadwell has not been available for comment and both the FBI and CIA have declined public comment on the matter.

Petraeus has made no public comment since he announced his resignation on Friday.

The affair has raised questions about whether U.S. national security was ever at risk and the timing of law enforcement and intelligence officials' revelation of the matter to the White House, as well as who knew about the investigation before last week's presidential election.

Meanwhile, a former spokesman for Petraeus during his time as an Army general has said the affair with Broadwell, an Army reserve officer who co-authored a glowing biography of him, began after Petraeus retired from the Army in August 2011 to lead the spy agency and ended four months ago by mutual consent.

Retired Colonel Steven Boylan, who was Petraeus' spokesman in Iraq and has spoken to the general since he resigned at the CIA, downplayed the question of whether U.S. security had been at risk. He said Petraeus never gave Broadwell classified information or communicated with her via his government email.

"My understanding is that she was only at the CIA twice. And at no time, based on conversations with him, did he provide her classified information, nor did she receive anything from him in that manner," Boylan said in an interview.

"My understanding is that they mutually determined that it was time to end it," he said, adding that Petraeus "knows he made a huge mistake" and is now trying to focus on his family. "It wasn't right. And it was done. That was about four months ago."

A law enforcement official, speaking on condition of anonymity, said Petraeus was first interviewed in connection with the FBI investigation during the week of October 28, about a week after Broadwell was questioned. The FBI informed Petraeus' boss, Director of National Intelligence James Clapper, in the early evening of Election Day, November 6.

Senior U.S. officials said Clapper then informed the White House's National Security Council staff of the issue and Petraeus' intention to resign on Wednesday, the morning after President Barack Obama was re-elected to a second four-year term. Obama was informed later that day, they said.

"Extremely poor judgment" 

Petraeus, a widely admired soldier-scholar credited with turning around the U.S. war in Iraq and who led NATO and U.S. troops in Afghanistan, announced his resignation in a letter to the CIA workforce on Friday, acknowledging "extremely poor judgment" in having an extramarital affair.

The person familiar with the investigation said Kelley initially approached a Florida field office of the FBI - not FBI headquarters - with a complaint of cyber-harassment. She had received numerous intimidating emails from a handful of different, opaque pseudonymous addresses.

The nature of the emails, according to the source, who was briefed on their contents, was "I know what you're doing" and similar suggestions that someone was onto Kelley. There was no explicit threat of violence.

Upon tracing them, the FBI found out that Paula Broadwell was behind them, this source said. They also found correspondence between Broadwell and Petraeus leading to the revelation of an affair between them.

High-level Justice Department officials were informed in late summer 2012 of an ongoing investigation involving Petraeus, according to a law enforcement official. This source would not name the Justice officials or say whether Attorney General Eric Holder was among them.

The Justice Department followed long-standing policy by not revealing the investigation to anyone outside the department, such as White House or congressional aides, this official said. It would be inappropriate and unfair to do so, and it might jeopardize any potential prosecution, the official added.

As the investigation moved into the fall, the focus was potential cyber-harassment by one woman against another woman.

Petraeus was thought of by investigators as a potential witness or party to the investigation, but he was never a target of investigators. Prosecutors considered whether the conduct in question constituted a crime of cyber-harassment under the law.

During their interviews with investigators, Broadwell and Petraeus both admitted to the affair, the official said. After the interviews, prosecutors decided they likely would not bring charges, based on the available evidence.

Another U.S. government official said the FBI investigation into the emails was fairly straightforward and did not require obtaining court orders to monitor the email accounts of those involved, including the personal email account of Petraeus. Rather, the official said, investigators reviewed the emails that Kelley had brought to their attention.

"There wasn't a court order," the government official said, adding that that action would have been a last resort when other avenues had been exhausted.

A source close to the Petraeus family confirmed that Kelley, who is 37 according to published reports, and her husband, Scott Kelley, a Tampa cancer surgeon, became friends with Petraeus when he was stationed at MacDill from 2008 until 2010 as commander of the U.S. military's Central Command, which runs operations in the Middle East and South Asia.

The Kelleys later visited the Petraeuses in Washington while on a trip to visit relatives.

The Kelleys did not answer phone calls to the number listed for the family's mansion-style home on Tampa's exclusive Bayshore Boulevard, close to the military base.

The Kelleys made the VIP guest list at military functions at MacDill and also hosted Petraeus and his wife at their home in 2010, for the city's annual Gasparilla pirate parade, according to a report at the time in the Tampa Bay Times.