An FBI agent investigating the 9/11 attacks reportedly lured an informant by fabricating an image of a 5-year-old child who looked like the suspect and his then-underage wife.

The Puerto Rican girl had converted to Islam and married Mohdar Abdullah on September 10, 2001, the night before the 9/11 attacks, under a tree at a Denny's parking lot.

"I knew I had a kid!," Abdullah said to an FBI agent.

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An FBI agent investigating the 9/11 attacks lured an informant by fabricating an image of a 5-year-old child who looked like the suspect and his then-underage wife.

Former FBI agent Daniel Gonzales, who worked out of the San Diego field office before retiring to help the family members of 9/11 victims, was one of the principal law enforcement officers assigned to find a potential connection with the Saudi kingdom — a campaign now known as "Operation Encore," according to a joint investigation by The New York Times Magazine and ProPublica.

One of the suspects Gonzales focused on was 22-year-old Mohdar Abdullah, a Yemeni from Italy who immigrated to Canada and then the US in 1998. After receiving a tip about Abdullah's connection to two 9/11 hijackers based in California, Gonzales tracked him down to a student parking lot near San Diego State University.

"What took you so long?" Abdullah said to Gonzales, according to the Times and ProPublica. "I thought you'd be all over me sooner."

In meetings at a local Denny's, Gonzales questioned Abdullah's connection with Khalid al-Mihdhar and Nawaf al-Hazmi, two of the hijackers who helped steer American Airlines Flight 77 into the Pentagon, killing 184 people.

A Denny's near San Diego State University in California. Google Maps

Abdullah, who had helped the two would-be hijackers acclimate to California where they would eventually undergo flight training, did not seem to be disclosing everything about his contacts, according to Gonzales. After interviewing Abdullah's acquaintances, the FBI discovered he appeared to be distraught leading up to the 9/11 attacks, and that he married a 16-year-old Puerto Rican girl he met just three months prior.

The Puerto Rican girl had converted to Islam and married Abdullah on September 10, 2001, the night before the 9/11 attacks, under a tree at parking lot at the same Denny's restaurant.

But before the agent could dig deeper into his history, Abdullah was arrested at gunpoint and whisked away to New York where he stood trial. FBI officials discovered Abdullah lied on his US visa application by claiming he was a refugee from Somalia, when in fact he was born in Italy. He was indicted for immigration fraud and jailed for two years before being deported to Yemen in 2004.

In 2006, Gonzales got a break. Abdullah submitted an immigration application to Canada, prompting officials there to notify the FBI and CIA. A Canadian intelligence official persuaded Abdullah, who was still irate from his run-in with US law enforcement, to accept Gonzalez's offer to speak for at least two minutes.

Gonzales brought with him a photo of a 5-year-old kid who resembled Abdullah and the Puerto Rican girl. Gonzales knew that the two had sexual intercourse, and had his supervisors sign off on a request for a graphics editor to create the picture.

"I knew I had a kid!," Abdullah reportedly said at the meeting.

Abdullah "started giving up nuggets" of information in the days ahead, according to Gonzales. While the leads Abdullah provided did not include any revelatory information, it did paint a fuller picture of how the hijackers were able to avoid detection before their attack.

Abdullah, who eventually moved to Sweden, was still irate about his experience with the US officials and refused to cooperate.

"The hijackers associated with many people in California," Abdullah said to the Times and ProPublica. "Nothing happened to any of them like what happened to me. This case keeps haunting me."

Families of the 9/11 victims have since made little progress in suing Saudi Arabia for their alleged ties to the hijackers - 15 of the 19 hijackers were Saudi nationals, and a Saudi official is believed to have tasked other Saudis to assist the terrorists, according to the FBI's own assessment in 2012.

Saudi Arabia has continued to deny involvement in the attacks.

Read the full New York Times Magazine and ProPublica report.