Then, he was gone.
New details in the case of Mr. Abdulmutallab, charged with attempting to bring down Detroit-bound Northwest Airlines Flight 253, have emerged suggesting that it was around this time that the young man met with the radical U.S.-born cleric Anwar al-Awlaki, according to a person familiar with intelligence shared among Arab states and a U.S. official.
The person familiar with Arab intelligence says Mr. Abdulmutallab met with a mysterious Saudi operative of al Qaeda.
Investigators in the U.S. and Yemen believe the meetings marked a critical turning point in Mr. Abdulmutallab's gradual transformation from pious Muslim to alleged terrorist. How and when his relationships were initially forged with al Qaeda and Mr. Awlaki, who has surfaced in multiple terror probes, is at the heart of the global scramble to trace Mr. Abdulmutallab's "radicalization"—and to determine how authorities could have missed the warning signs.
Through most of his life, the Nigeria-born Mr. Abdulmutallab came off as a religious and inward young man, so opaque as to be virtually unknowable. He was intense and serious about Islam, but in a way that acquaintances judged to be within the mainstream.
People familiar with the investigation say he began to quietly reach out to political extremists as a college student in London from 2005 to 2008, then apparently embedded more deeply with them as he hop-scotched around Africa and the Middle East. They say it was during his time in London that he was likely first exposed to Mr. Awlaki via the cleric's rabble-rousing anti-Western sermons on the Internet. He is believed to have reached out to the cleric at some point, but it couldn't be learned when that first contact was attempted or whether Mr. Awlaki responded.
This account of Mr. Abdulmutallab's childhood and journey over the past few years is based on several dozen interviews with friends and associates, as well as government officials examining his movements in the U.S., Europe, Africa and the Middle East.
Mr. Abdulmutallab, 23, is the son of Alhaji Umaru Mutallab, recently retired chairman of First Bank of Nigeria PLC and one of the country's most prominent businessmen. People who encountered Mr. Abdulmutallab at various stages of his life describe him as a young man who studied Islam, prayed frequently and radiated loneliness. As a boy in Kaduna, Nigera, Mr. Abdulmutallab earned the nickname "ustaz," or "scholarly man." He steered clear of the country-club parties and polo matches frequented by other wealthy kids.
He was "a nice boy who had no friends," recalls Musa Umar Dumawa, director of the Islamic school Mr. Abdulmutallab attended in Kaduna. Yet in Internet postings attributed to him as a teenager, he also fretted about his isolation: "Either people do not want to get close to me as they go partying and stuff while I don't, or they are bad people who befriend me and influence me to do bad things."
From childhood on, Mr. Abdulmutallab was exposed to circumstances that could have shaped his political views. Kaduna was home to growing anti-Western sentiment among Muslims, fueled in part by clashes with Christians that erupted in 2000, when the local governor considered imposing Sharia, or Islamic law.
After a few years at boarding school in Togo, Mr. Abdulmutallab in 2004 ventured to Yemen, where a growing number of Islamic extremists have been relocating from Pakistan, Iraq and Saudi Arabia. From fall 2004 to spring 2005, he studied at the San'a Institute for Arabic Language, according to Mohammed Al-Anisi, the institute's director.
"He knew how to read and write in Arabic because he had learned to read the Quran being a Muslim, but his speaking abilities were very limited," recalls Mr. Anisi.
Mr. Abdulmutallab began his year in San'a shortly after Mr. Awlaki, the radical cleric, returned to the city after 14 years in the U.S. and London. While Mr. Abdulmutallab was studying Arabic in San'a's Old City, Mr. Awlaki was making a name for himself as a vibrant newpreacher. He gave regular Friday sermons at the Yehya al-Ghader mosque on the city's Western periphery. He lectured at the Al Iman University, founded by Sheikh Abdel Majeed Zindani in 1995, who both the U.S. Department of the Treasury and the U.N. Security Council have named as an affiliate of al Qaeda.
There is no evidence to suggest that Mr. Abdulmutallab ever attended Mr. Awlaki's sermons or lectures or met the cleric during this period.
Mr. Abdulmutallab harbored dreams of studying engineering in the U.S. at Stanford University or the California Institute of Technology, but in the fall of 2005, he enrolled in the mechanical engineering program at University College London. Internet postings from early 2005 that appear to have been written by Mr. Abdulmutallab show a craving for the fellowship of a student Islamic society. At UCL, he quickly hooked up with the university's Islamic group.
There, Mr. Abdulmutallab was often seen dressed in traditional white robe and skull cap. He arrived at class on his own, says Derek Wong, a fellow student. Others recall he was friendly but declined invitations to drink or socialize. Michael Kangawa, a student, says Mr. Abdulmutallab invited him to talks on Islam, none of which "sounded sinister in the slightest."
Through the UCL Islamic Society, for which he served as president in 2006 and 2007, Mr. Abdulmutallab became involved in politics. One former student recalls that in the summer of 2006 Mr. Abdulmutallab solicited signatures for a petition against the Israeli occupation of Palestinian lands and against Western support for Israel. "He was very passionate and very articulate," this person says.
Qasim Fariq, Mr. Abdulmutallab's predecessor as the society's president, says he saw no signs of a budding militant. "If he'd had radical views, that would have raised a question mark about his suitability to be president," says Mr. Fariq. "He never expressed any extremist inclinations."
U.K. intelligence agencies, now combing through his history, say that Mr. Abdulmutallab was flirting with a more radical form of Islam. While a student, people familiar with the matter say, he made contact with several extremists who were being monitored by the security services. Yet security agencies have so far found no evidence that he was contemplating violence while in the U.K. or posed a threat to national security.
"It looks pretty aspirational, and it doesn't look as if he got particularly far," a British official says. While in the U.K., he gave the impression of "a young guy who's trying to start out on a journey.... We see many people who start out on that journey and very few of them reach the point where they are willing to blow up people on tube trains."
Mr. Abdulmutallab's movements became harder to track after he graduated from UCL in June 2008. He appears to have cut himself off from college acquaintances. "In December, I sent him an instant message when I saw he was online, but he never replied," says Mr. Fariq. "I was surprised he'd cut off contact so abruptly."
Mr. Abdulmutallab bounced around the world. His application to obtain a visa to travel to the U.S. raised no red flags, and he visited Houston—home to an estimated 100,000 Nigerian immigrants—in August 2008. He stayed for about two weeks, attending an Islamic seminar run by a nonprofit educational group called the Al Maghrib Institute and staying at a Sheraton hotel on the outskirts of downtown.
In October, he turned up in Nigeria. There, he approached Abdulkareem Durosinlorun, the director of a small Islamic primary school in Kaduna, with a proposal to teach a course on Prophetic medicine, the ways of healing according to the Prophet Muhammad.
"He spoke about combating demons of power, or money," says Bilquees Abdul Azees, who attended the two-day course. "His solution was that if you have faith in Allah, you will persevere."
In January 2009, Mr. Abdulmutallab arrived in Dubai with his father, according to a person familiar with intelligence shared between Arab governments investigating the Nigerian's movements. He applied for a student visa and enrolled at University of Wollongong, the Dubai-based campus of the Australian institute, to pursue a degree in international business, which involves courses in finance, accounting and human resources.
He lived in student housing, played basketball on the side, and struck fellow students and faculty as diligent and quiet. University President Robert J. Whelan says Mr. Abdulmutallab was a "hard-working" student who scored "above-average" grades.
In April 2009, he applied for a visa to attend an eight-day course provided by Discovery Life Coaching based in east London. The U.K. Border Agency refused the application because Discovery Life didn't hold valid accreditation as an educational institution and wasn't eligible to sponsor international students in Britain. Attempts to find a company called Discovery Life in that area were unsuccessful.
He completed only two semesters in Dubai, failing to pay his fees for what would have been his third and final semester before graduating. During his final days in Dubai in early August, he sent his father an SMS text saying he was headed to Yemen to study Arabic, according to the person familiar with Arab intelligence sharing. He left the country Aug. 4 "and never showed up again" in Dubai, this person said.
Near the start of the Muslim holy month of Ramadan, which began Aug. 22, Mr. Abdulmutallab returned to the language institute in Yemen where he had studied as a teenager. Mr. Anisi, the institute's director, says the young man appeared more serious, withdrawn and pious than the student who had left four years earlier.
People who were there say he stayed no more than 10 days before leaving. "He said it was Ramadan and he wanted to focus on praying," said one student.
Matthew Salmon, a 27-year-old Canadian student, lived next door to Mr. Abdulmutallab in this period. They talked about religion, with Mr. Abdulmutallab gently proselytizing and focusing on Quranic verses that spoke of tolerance for Christians and Jews. "More than anything else, he seemed like someone who had found some peace in the religion he subscribed to. ... He was honest, he was happy, and there was absolutely no malice in the guy that I could detect."
In early September, Mr. Salmon had a final conversation with him. "I asked him how long he planned on staying in Yemen, and he said a month or two depending on how long the money held up and how his studying progressed. The next day he was gone, his room was empty and that was the end of it."
Yemeni officials say Mr. Abdulmutallab left San'a and traveled to the rugged tribal-controlled southern province of Shabwa, where al Qaeda has a strong presence and where Mr. Awlaki has lived at least the past two years. There, Mr. Abdulmutallab met with al Qaeda leaders in Yemen and "likely" Mr. Awlaki, according to Yemen's government.
The person familiar with intelligence sharing among Arab states and a U.S. official say Mr. Abdulmutallab met face-to-face with Mr. Awlaki, but it's unclear where or when. This person says Mr. Abdulmutallab befriended an al Qaeda operative while attending a mosque in downtownSan'a. A U.S. security official says the mosque has been frequented by al Qaeda members. "Slowly, slowly, he started liking them, and he got their trust," this person said of Mr. Abdulmutallab.
His precise itinerary after leaving Yemen is in dispute. What is known is that he arrived in Ghana in early December, staying about two weeks and buying an airline ticket for travel later in the month, according to the Ghana government. On Dec. 24, he flew to Lagos and proceeded to Amsterdam after a brief stopover. On Dec. 25, he boarded Flight 253 in Amsterdam, headed for Detroit.