Darren's daughter, Raina, was 2 when her father died, but she says she remembers him holding her. The CIA Officers Memorial Foundation has supported the family financially, as it seeks to do with all families of fallen officers.

"I think that it's important for people to know that there are people out there in the shadows that are doing behind-the-scenes work that they don't even realize," Racheal LaBonte, Darren's widow, told NBC News' Savannah Guthrie for the "TODAY" show. "They are the sheepdogs to the sheep. There is danger that is lurking in the shadows, and there are people out there that are protecting every single one of us."

Darren had a reverence for the ancient Spartans, and "he talked about wanting to be the one standing on the ramparts protecting America," said Marc Polymeropoulos, a recently retired CIA officer who served alongside him. "He did that as well as any officer I ever worked with."

Darren LaBonte came to the CIA later in life than many other recruits. He grew up all over the country because his father moved the family every few years to keep up with his career at General Electric. A star athlete in high school, he turned down an offer to sign with a minor league affiliate of the Cleveland Indians, his parents said, and instead joined the Army.

"He wanted to serve," said his mother, Camille. "He cared a lot about everything."

He became an elite Army Ranger, met and married Racheal, left the military in 1999 and became a police officer.

After he watched the Twin Towers collapse on Sept. 11, 2001, Darren wept, his mother said.

Darren LaBonte when he was an FBI agent. Courtesy of the LaBonte family

Then he began trying to figure out how he could get in the fight. He joined the U.S. Marshals Service and then became an FBI agent. With his Ranger background, and having won awards in his class at the FBI training academy, he was assigned to an elite detail investigating organized crime in New York City. But that didn't scratch the itch to strike against those who attacked America.

In 2006, the CIA called.

Let our news meet your inbox. The news and stories that matters, delivered weekday mornings. This site is protected by recaptcha

LaBonte initially joined the agency's paramilitary arm, the Special Activities Division, which often conducts joint operations with Navy SEALs and the Army's Delta Force. He deployed to Afghanistan and Iraq, his family said.

After his daughter was born, he accepted a posting in Amman, Jordan, to work as a case officer. There, he became close with Ali bin Zeid, a Jordanian intelligence officer and member of the royal family.

As Joby Warrick writes in his exhaustively reported book on the tragedy, "The Triple Agent," it was Zeid who initially recruited the Palestinian-Jordanian doctor, an avowed extremist, as an informant. But the CIA took over the case, and the man was to have been Darren's asset if all had gone as planned.

That wasn't to be.

The Jordanian doctor had led the CIA to believe that he had infiltrated al Qaeda as a double agent, having gone so far as to provide video suggesting that he had gotten close to the terrorist group's No. 2, Ayman al Zawahiri.

In truth, it was a diabolically clever ruse — he was loyal to al Qaeda all along.

CIA officials grew eager to meet with the doctor, and word of a possible spy within al Qaeda's ranks had gone all the way to President Barack Obama, a dynamic that put enormous pressure on the line officers managing the case. By the time a meeting was set for Dec. 30, 2009, at remote Camp Chapman in Khost province along the Afghanistan-Pakistan border, a number of senior officials were involved in the planning — too many, the investigation would conclude.

The base chief was Jennifer Matthews, a mother of three, usually a desk-bound analyst, one of the agency's foremost al Qaeda experts but lacking field experience. Matthews and other CIA officials decided that the doctor should be made to feel welcome. He would not be searched, and he would be greeted by a large number of CIA officers. Matthews even had a cake baked to present him in honor of his birthday, Warrick writes.

LaBonte, who had flown in from Jordan with Zeid, expressed reservations about the meeting to his superiors at the CIA — and also to his father.

"I said, 'Why not just call it off?'" Dave recalled, but agency managers decided the risks were worth taking. No one involved, the investigation found, had imagined a suicide bomb, something that had never happened in the history of agent recruitments.

As reported by Warrick and depicted in the movie "Zero Dark Thirty," the Jordanian doctor was not patted down before he was driven onto the base, where he stepped out of the car and detonated his shrapnel-filled device in front of a group of Americans. Along with Darren, those killed were Matthews, Elizabeth Hanson, Scott Michael Roberson, Harold Brown Jr., Dane Clark Paresi and Jeremy Wise. Zeid and an Afghan security officer were also killed, and a number of other CIA officers were grievously wounded.

The investigative report that emerged 10 months later was scathing, but the CIA director, Leon Panetta, decided not to discipline anyone.

"This is a case where there are some systemic failures where all of us have responsibility, and all of us need to fix it," he said at the time.

Racheal, Raina and LaBonte's parents and brother were vacationing at a Tuscan villa, waiting for Darren to join them after the meeting. The farmhouse was so remote that the CIA couldn't find it. The Amman station chief had to break the news by phone.