WASHINGTON >> Ex-CIA director David Petraeus has told friends he was shocked to find that his biographer and girlfriend, Paula Broadwell, was suspected of sending anonymous, threatening emails to a Petraeus friend she saw as a romantic rival.

A close Petraeus associate said today that FBI investigators told Petraeus that Broadwell sent anonymous emails to Jill Kelley, a Petraeus family friend from his time at Central Command in Tampa, warning her to stay away from him. The Petraeus associate spoke on condition of anonymity to discuss confidential conversations with Petraeus. The CIA director resigned last week after confessing to the affair.

Petraeus was not shown the emails, but was told the tone and content seemed threatening to Kelley, prompting her to report them, the close Petraeus associate said. That triggered the investigation that led the FBI to Broadwell and evidence of her affair with Petraeus.

The affair began in 2011, two months after he became CIA director, a friend and former top aide said today. The case has sparked an uproar in Congress over FBI investigative tactics and complaints by lawmakers they weren’t told soon enough about the probe rocking the intelligence and law enforcement establishment.

Petraeus, who resigned last week as the nation’s head spy, and his family are said to be devastated over the affair, especially his wife Holly, who “is not exactly pleased right now,” said Steve Boylan, a friend and former Petraeus spokesman who spoke to Petraeus over the weekend.

“Furious would be an understatement,” Boylan told ABC’s “Good Morning America.” He said Petraeus ended the affair four months ago.

Members of Congress said they want to know more details about the FBI investigation that revealed the extramarital affair between Petraeus and Broadwell. They questioned when the retired general popped up in the FBI inquiry, whether national security was compromised and why they weren’t told sooner.

Petraeus, 60, quit Friday after acknowledging the affair. He has been married 38 years to Holly Petraeus, with whom he has two adult children, including a son who led an infantry platoon in Afghanistan as an Army lieutenant.

Broadwell, a 40-year-old graduate of the U.S. Military Academy and an Army Reserve officer, is married with two young sons.

According to a senior U.S. military official, Kelley, 37, who lives in Tampa, Fla., and serves as an unpaid social liaison to MacDill Air Force Base in Tampa, where the military’s Central Command and Special Operations Command are located. Staffers for Petraeus said Kelley and her husband were regular guests at events he held at Central Command headquarters. 

A U.S. official said the coalition countries represented at Central Command gave Kelley an appreciation certificate on which she was referred to as an “honorary ambassador” to the coalition, but she has no official status and is not employed by the U.S. government.

In a statement Sunday, Kelley and her husband, Scott, said: “We and our family have been friends with Gen. 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.”

The military official who identified Kelley spoke on condition of anonymity because he was not authorized to publicly discuss the investigation. He said Kelley had received harassing emails from Broadwell, which led the FBI to examine her email account and eventually discover her relationship with Petraeus. It was not clear what led Broadwell to send the emails to Kelley.

The FBI contacted Petraeus and other intelligence officials, and Director of National Intelligence James Clapper asked Petraeus to resign.

A former associate of Petraeus confirmed the target of the emails was Kelley, but said there was no affair between the two, speaking on condition of anonymity to discuss the retired general’s private life. The associate said Kelley and her husband were longtime friends of Petraeus and his wife.

Boylan said today that Petraeus is keenly aware that he has injured his family while losing “one of the best jobs he ever had. He’s devastated.” The affair with Broadwell started about two months after Petraeus took the CIA post, Boylan said. Petraeus became CIA director in September 2011.

Petraeus’ affair with Broadwell will be the subject of meetings Wednesday involving congressional intelligence committee leaders, FBI deputy director Sean Joyce and CIA deputy director Michael Morell.

Petraeus had been scheduled to appear before congressional committees on Thursday to testify about the Sept. 11 attack on the U.S. Consulate in Benghazi, Libya, that killed four Americans, including U.S. Ambassador Chris Stevens. Morell was expected to testify in place of Petraeus, and lawmakers said he should have the answers to their questions. 

Clapper was told by the Justice Department of the Petraeus investigation last week at about 5 p.m. on Election Day, and then called Petraeus and urged him to resign, according to a senior U.S. intelligence official who spoke on condition of anonymity because he was not authorized to discuss the investigation publicly.

FBI officials said the congressional committees weren’t informed until Friday, one official said, because the matter started as a criminal investigation into harassing emails allegedly sent by Broadwell to Kelley.

Concerned that emails Petraeus exchanged with Broadwell raised the possibility of a security breach, the FBI brought the matter up with him directly, according to the official, who spoke on condition of anonymity because he was not authorized to publicly discuss the investigation.

Petraeus decided to quit, though he was breaking no laws by having an affair, officials said.