Editor's note: This article, the second of two parts, is the result of a 10-month CNN investigation into the case of Bryant Neal Vinas, an American al Qaeda recruit featured in the one-hour documentary "American Al Qaeda" to air Saturday, May 15, and Sunday, May 16, at 8 p.m. and 11 p.m. ET. The documentary airs on CNN International on Saturday , May 22 at 8 a.m. ET and Sunday, May 23 at 3 p.m. ET. (Read Part 1 here.)

(CNN) -- On the eve of the sixth anniversary of the September 11, 2001, terrorist attacks on New York and Washington, Bryant Neal Vinas boarded a flight from New York to Lahore, Pakistan.

The 24-year-old lifelong New Yorker had enlisted in the Army after graduating from high school, in part because of that seminal event. Now he was a recruit of a different kind, on his way to join al Qaeda in waging holy war against U.S. troops.

A Muslim convert now known as Ibrahim, he would eventually earn a fighting name: Bashir al Ameriki, "the American."

But when Vinas landed in Lahore on September 12, 2007, he had little idea how to achieve his goal. He had never been to Pakistan.

He had no connections to jihadists in the country, and though he had started to learn Arabic, he did not speak Urdu or Pashto, the country's main languages.

He had left the United States without telling his parents or sister where he was going. And he had hidden his true intentions from many of his close Muslim friends on Long Island.

But investigators suspect two of Vinas' friends at the Islamic Thinkers Society, a pro-al Qaeda extremist organization in New York, knew what he was up to.

One of those, according to U.S. counterterrorism officials, was Ahmer Qayyum, whose hometown was Lahore.

Vinas had planned to travel to Pakistan with him, but Qayyum was, by his own account, delayed a few days.

"We had planned to come back, like, together but ... I had to, like, work for a few extra days in the [United] States ... and he arrived in Lahore before me," Qayyum told CNN.

He denied knowing Vinas' intentions and said he believed his friend was merely on his way to study the Quran at a madrassa, or religious school.

Within a few days, Qayyum joined Vinas in Lahore. Vinas, Qayyum said, was staying in a guest house in the Firdous Market district, a bustling neighborhood near the main cricket stadium.

As Vinas acclimated to the hot, crowded city, Qayyum said he spent time with his friend, joining him on occasion to pray in mosques.

After several weeks, Qayyum said, Vinas left to attend a madrassa in Peshawar, near the border with Afghanistan. Qayyum said he helped Vinas arrange his trip to the madrassa, but denied Vinas was planning to fight jihad.

But counterterrorism officials told CNN they believe Qayyum is the "fixer" Vinas referred to in an interview with authorities after his arrest. In that interview, Vinas told officials that a "friend from New York ... agreed to help him and introduce him to people who could assist him in getting to Afghanistan."

In that question-and-answer session, held in the presence of Belgian magistrates in the FBI offices in New York in March 2009, Vinas provided details about his time in Pakistan.

The Belgian document, which was entered into evidence in a recent trial of an alleged Belgian al Qaeda cell in Brussels, was provided to CNN by a defense lawyer in the case and authenticated by a U.S. prosecutor and Vinas' defense lawyer.

The following account is based on the Belgian document, as well as interviews with counterterrorism agents and others close to the investigation.

Much of it is drawn from Vinas' own statements to investigators, contained in the Belgian document. In late September 2007, when Vinas traveled to Peshawar, a violent Islamist insurgency was brewing in the North West Frontier Province and tribal areas along the border with Afghanistan.

Two months earlier, Pakistani security services had stormed the Red Mosque in Islamabad, killing many Taliban militants who had taken control of the compound, sparking a wave of suicide bombings and attacks across Pakistan.

Deep inside Pakistan's Federally Administered Tribal Areas, al Qaeda had again built up the capability to launch an attack on the United States, according to a U.S. National Intelligence Estimate published that summer.

After a series of meetings, Vinas and his New York friend found someone who could connect Vinas with Shah Saab, a militant commander conducting armed forays into Afghanistan from Pakistani territory.

Saab took Vinas to his camp in Mohmand in the tribal areas to prepare for a raid against American troops across the border in Afghanistan.

"The group then crossed the border to get into the Konar Province in Afghanistan," according to the Belgian document. "They were a group of 10 to 20 men. The group separated into two further groups; one led a ground attack with guns and rocket-propelled grenades against an Afghan military base.

"Vinas was part of the second group who planned to climb the mountains and stockpile mortars to launch a new attack on an American base," the document says.

"The group eventually decided not to launch the mortar bombs themselves because planes were circulating over the region -- and fearful of being attacked the next night -- the group including S.S. [Shah Saab] returned to Pakistan."

Ready to die

Back in Mohmand, one of Saab's men asked Vinas to become a suicide bomber.

He accepted.

Not only did he want to kill the servicemen of his own country, but he also appeared to be willing to give up his own life to do it.

U.S. counterterrorism officials believe this may have been a test of loyalty for Vinas -- a way to prove he was not an American spy.

"You're going to go through multiple paths, multiple doors before someone trusts this person," said Phil Mudd, deputy head of the FBI's National Security Branch at the time of the Vinas investigation.

Mitch Silber, director of intelligence analysis for the New York Police Department, believes it was a crucial steppingstone for Vinas.

"His offer to become a suicide bomber obviously gave him some standing and facilitated his ultimate linkup to al Qaeda," Silber said.

After agreeing to become a suicide bomber, Vinas was sent back to Peshawar to receive more instruction. It is possible that Vinas' militant handlers were hatching more ambitious plans for him.

But Vinas said Saab told him that he needed more religious instruction before he could become a suicide bomber.

The young American was growing frustrated. That feeling was shared by another member of Saab's militant group, whose identity CNN was unable to learn.

Together, the two resolved to find the contacts necessary in Peshawar to receive training in the tribal areas of Pakistan.

At first, they were unsuccessful. A series of promises were made, but each time, their contacts did not deliver. Fed up, Vinas set off on his own for the tribal areas of Pakistan.

To evade Pakistani security, Vinas wore a burqa, the head-to-toe covering worn by some Afghan and Pakistani women. But he failed to connect with al Qaeda and returned to Peshawar, disappointed.

With his poor Arabic, Western appearance and lack of contacts who could vouch for him, it was difficult at first for Vinas to win the trust of fighters in the tribal areas.

On his second trip, he was almost killed by militants but managed to talk them into letting him go. Eventually, Vinas met a militant in Peshawar who did have contacts within al Qaeda.

Again, he set off for the tribal areas and made contact with al Qaeda members in North Waziristan. The fighters there, he said, were from places such as Yemen, Saudi Arabia and Kuwait. He became friendly with one Yemeni who agreed to vouch for him so he could secure membership in al Qaeda.

In March 2008, Vinas became a full-fledged member of al Qaeda, pledging to obey all orders.

"What characterized you being an al Qaeda member was the fact you followed the orders given to you by leaders ... [you were] totally committed," Vinas later stated.

A new fighting name, "Bashir al Ameriki," completed Vinas' metamorphosis from all-American kid to al Qaeda recruit.

His persistence had paid off.

"That trait would make him potentially very dangerous if he had decided to do some kind of terrorist plot in the West, because he would not have given up," said Marc Sageman, who advised the New York Police Department on the Vinas case.

As an al Qaeda recruit, Vinas found new friends, too. The child of a broken home, Vinas had always treasured his friendships, and in the mountains of Waziristan, he found camaraderie with other fighters.

He hung out with a band of European militants who had traveled to the tribal areas from Belgium and France. While undergoing training, he lived with one of them, Hicham Zrioul, a Belgian-Moroccan taxi driver from Brussels.

After a hard day's training with al Qaeda, Vinas and Zrioul would unwind in their small mountain shack by watching jihadist videos on a Dell computer Zrioul had acquired.

Between March and July 2008, Vinas said he attended three al Qaeda training courses focused on weapons, explosives and rocket-based or propelled weaponry.

During these classes, attended by 10 to 20 recruits, Arab instructors taught Vinas how to handle a large variety of weapons and explosives, some of them of military-grade sophistication.

Vinas said he became familiar with seeing, smelling and touching explosives such as TNT, as well as plastic explosives, including the kind U.S. authorities say was used in al Qaeda's attack on the USS Cole in 2000.

Vinas also learned how to make vests for suicide bombers. The terrorist skills Vinas acquired made him a potentially deadly threat if al Qaeda decided to use him for an attack in the United States.

"Once they go out and gain that operational training -- whether communication security or how to build a device -- their potential for lethality is much greater," said Mudd, the former FBI official who supervised the Vinas investigation.

During a mountain walk one day, Zrioul told Vinas about a planned attack on the Brussels metro, which he called a soft target because of poor security. Vinas said Zrioul also raised the possibility of launching an attack on a European football stadium.

(A senior Belgian intelligence official told CNN that Belgian security services only learned about these conversations in March 2009, after Vinas met with Belgian prosecutors in New York. Although concerned, Belgium's intelligence service concluded that no concrete plot had likely existed).

Despite the threat of U.S. drone strikes in the tribal areas, Vinas' handlers allowed him to travel widely, perhaps because curiosity had grown about al Qaeda's valuable new American recruit.

But providing the young American with a window-seat view of their strongholds was a decision his handlers would later regret. His potential value to the intelligence services of his own country was growing by the day.

During his travels, Vinas met fighters and leaders from an array of al Qaeda-affiliated groups. At a tribal gathering in North Waziristan, he was introduced to Baitullah Mehsud, then leader of the Pakistani Taliban. (Mehsud was killed by a drone in August 2009.)

Vinas met former bodyguards of Osama bin Laden and a veritable who's who of al Qaeda's top commanders, including the Egyptian operative Mustafa Abu al Yazid, one of al Qaeda's founders, and Attiya Allah, a Libyan al Qaeda ideologue, who helped mentor Vinas.

But the American recruit was told nobody got to meet bin Laden. In July 2008, Vinas completed his final training course and was judged qualified to participate in a missile strike against U.S. troops in Afghanistan.

After weeks waiting for orders,Vinas was dispatched with a group to the Afghan border. It was September 2008, almost exactly a year since Vinas had arrived in Pakistan.

As he hiked through the high mountain passes, loaded down with rockets, he was for a second time close to fulfilling a goal that had become an obsession: killing the soldiers of his own country in the name of jihad.

When Vinas' group reached a site overlooking an American base on the Pakistan-Afghanistan border, they readied their missiles for launch.

Then, things fell apart.

"The first attack was not launched because of radio communication problems," Vinas would later tell authorities, "but a few days later, I took part in firing rockets at an American base. Although we intended to hit the military base and kill American soldiers, I was informed that the rockets missed and the attack failed."

Afterward, Vinas returned to the al Qaeda encampment in the mountains of Waziristan. U.S. counterterrorism officials said they believe that mission may have been al Qaeda's final test for their American recruit.

"If you want to go to a further level of training, being tested by proving that you'll engage in a fight against American or other forces in Afghanistan is a pretty good test," said the FBI's Mudd.

Al Qaeda leaders now felt comfortable enough to have detailed conversations with Vinas about plans to attack the West, including the United States.

"I consulted with a senior al Qaeda leader and provided detailed information about the operation of the Long Island Rail Road system, which I knew because I had ridden the railroad on so many occasions," Vinas later testified in a U.S. court.

"The purpose of providing information was to help plan a bomb attack of the Long Island Rail Road system."

While Vinas discussed that plot with al Qaeda leaders in September 2008, three young men arrived in the tribal areas from the United States. They, like Vinas, were allegedly intent on fighting American troops in Afghanistan.

Their ringleader was Najibullah Zazi, a Denver, Colorado, taxi driver who had gone to high school in Queens, New York, just a few blocks from where Vinas had lived when he was very young.

Zazi later admitted that he received bomb-making training in al Qaeda camps that fall and was persuaded by al Qaeda to launch attacks on the United States.

In September 2009, the FBI thwarted Zazi's plot to conduct suicide bombings on subway cars in New York, just days before it was about to go into operation, according to court documents outlining Zazi's guilty plea.

While CNN has not been able to establish whether Zazi and Vinas met, the two appear to have been in the same militant circles in the tribal areas in fall 2008, according to European counterterrorism sources.

Vinas, they said, was in touch with an al Qaeda member believed connected to Rashid Rauf, the British al Qaeda operative who allegedly orchestrated Zazi's plot against New York.

Counterterrorism officials said they believed al Qaeda leaders probably would have eventually asked Vinas to take part in an attack on U.S. soil. No evidence has emerged, however, that they did so before his arrest.

Vinas "must have been for them a great opportunity they wanted to exploit," said Silber, of the NYPD, because of his appearance and U.S. passport.

"I think his main value to al Qaeda is the same they've been looking for, really, going back to 9/11," Silber said. "In the sense, who can operate for al Qaeda in the West. Here's an individual who has a lot of appeal to you, who's sort of just shown up on your doorstep."

A personal mission

Vinas stayed in the al Qaeda encampments in the tribal areas until early October, then set off back to Peshawar to devote some time to a more personal mission: He wanted to find a wife.

He called his friend, Ahmer Qayyum, in Lahore to tell him the news.

"He gave me a call a couple of times, [to say] like I'm OK, you know. He even said, 'I'm going to get married.' "

But as Vinas walked around the bustling bazaars of Peshawar, U.S. intelligence agencies were closing in on him.

A senior U.S. counterterrorism official said intelligence agencies had begun tracking Vinas some time before his arrest.

He would not reveal the nature of the tracking or when it began.

That month, FBI agents visited Vinas' father, Juan Vinas, on Long Island, telling him they believed his son was in Pakistan.

But, according to Juan Vinas, they masked their true reasons for inquiring about his son.

The FBI agents then asked if they could search his son's computer and look through his e-mail, which Juan Vinas allowed.

On or around November 14, 2008, Vinas' al Qaeda conspiracy came to an end, according to court papers.

After a tip from their U.S. counterparts, Pakistani security services arrested Vinas in Peshawar and transferred him into American custody.

CNN has not been able to establish the exact date of his arrest.

Vinas' friend Qayyum said he learned of the arrest through the grapevine. He was told Vinas was picked up by Pakistani police in a Peshawar market.

"When something like this happens, I mean a foreigner, you know, getting arrested, it circulates, you know. It's big news," Qayyum said.

Back in the United States, Vinas' father received a call from the FBI, saying that Pakistani authorities had apprehended his son.

"They made it sound like it was for a visa violation and that he would be deported," Juan Vinas recalled.

After that, he said, the FBI did not return any of his calls.

On November 22, Vinas was arraigned in secret in federal court in Brooklyn, New York, on terrorism charges.

Although he initially pleaded not guilty, Vinas started cooperating with U.S. investigators. Just days after his arraignment, federal officials issued an intelligence bulletin warning that al Qaeda had discussed attacking transit systems in the New York metropolitan area, including the city's subway.

This led New York authorities to step up security on the city's mass transit systems. A senior counterterrorism official told CNN that information about the al Qaeda plot came from Vinas and that authorities had acted out of an "abundance of caution."

After Vinas started cooperating, he provided "extremely helpful information" in targeting al Qaeda operatives in the tribal areas of Pakistan.

"Just by talking about what he saw, telling us what houses and streets operatives were living in, identifying how al Qaeda runs its courier networks, he has provided us priceless information," a senior U.S. counterterrorism official told CNN.

"This was actionable intelligence."

In recent years, the CIA has carried out a covert aerial campaign targeting al Qaeda and the Pakistani Taliban in the Federally Administered Tribal Areas using unmanned drones.

Vinas' arrest coincided with an intensification of the CIA's drone campaign in the tribal areas of Pakistan, strikes that have killed more than a dozen leading al Qaeda operatives in the last two years.

U.S. counterterrorism officials will not comment on whether intelligence from Vinas helped with any specific strike. What officials do acknowledge, however, is that Vinas became a powerful resource in the U.S. war against al Qaeda.

"His intelligence was not just useful in the first few weeks after his capture, but for months afterward," a senior U.S. counterterrorism official told CNN. "Vinas was as valuable as having our own agent penetrate al Qaeda. In many ways, the end result was like undertaking a classic intelligence operation."

Not everybody welcomed his cooperation with U.S. authorities.

Yousef al Khattab, the chief ideologue of the Islamic Thinkers Society, said he feels betrayed by Vinas.

"For informing on the people that are fighting in Afghanistan," Khattab said, "I call him a coward."

With such a prized asset in custody, authorities took extraordinary measures to keep Vinas' arrest secret. All court proceedings were kept closed on national security grounds, and his family members were kept in the dark about his arrest.

On January 28, 2009, in a closed-door session in federal court in Brooklyn, Vinas pleaded guilty to all charges against him: conspiracy to murder U.S. nationals, conspiracy to provide material support to a foreign terrorist organization and receiving military-type training from a foreign terrorist organization.

Vinas faces a maximum of life in prison but could receive a lower sentence if he continues to cooperate.

Sources told CNN that Vinas has come away from his radical views and is cooperating willingly.

On July 22, 2009, news broke of Vinas' arrest after federal authorities unsealed his guilty plea. The revelation that he helped al Qaeda plot a bomb attack in New York came as a shock to his family.

At first his mother could not believe the news.

"He's accused of such horrible things," she told CNN.

In prison, Vinas became increasingly restless and lonely. In August 2009, he wrote a letter to his friend Alex Acevedo, begging him to write back with news.

"You ever see the movie Groundhogs day, [sic] well that's how I feel like every day," Vinas wrote.

Acevedo did not write back.

"I'm pissed off with him. ... It's wrong. He could have been killing his own people on that train," he said.

Other friends of Vinas', however, feel no anger about what he did.

"I feel proud of him. I respect him. ... If I ever meet him, I'm going to hug him. I'm going to love him for what he did," said Ahmer Qayyum, the former Islamic Thinkers Society devotee.

"And if my message can reach him, you know, I mean I just want him to stay strong. I don't think the American evil empire is going to last too long now. Inshallah."

For Vinas' mother and sister, the shock of his arrest has been replaced by terrible disappointment and flashes of anger.

Vinas was no different from most other American teenagers, they said. But now, they feel like they don't know him anymore.

If all this can happen to them, they fear it can happen to another American family.