It was midsummer in suburban Denver when an unassuming, bearded man pushed a red shopping cart between shelves stacked with hair coloring and nail polish remover.
By the time Najibullah Zazi checked into a nearby hotel suite with a kitchen in September, he had at least 18 bottles of peroxide-based hair lighteners and pages of notes for how to turn the beauty products into bombs, authorities say.
Prosecutors say the otherwise mundane movements of the 24-year-old airport shuttle driver — who sold Wall Streeters coffee for years from his cart in downtown Manhattan and returned to the spot, not far from ground zero, on his recent two-day trip to the city — masked a dire terrorist threat.
The peroxide purchases, Zazi's prayer at a local mosque on the eve of his planned attack and a cross-country trip back to his Queens neighborhood, authorities say, are steps in his evolution from a struggling immigrant who was a teenager on Sept. 11, 2001, to a full-blown terrorist plotting to bomb the city on the attacks' eighth anniversary.
Many questions about charges that Zazi became a terrorist over the past year — and who was helping him — remain unanswered. Prosecutors refer to "others" who accompanied him on an August 2008 flight to Pakistan for terrorism training, by which time he had come to authorities' attention, and who shopped with him in Aurora, Colo., for chemicals that could be turned into bombs. But neither accomplices nor explosives has turned up; Zazi's father and a Queens imam face charges only of lying to terrorism investigators, and they deny the allegations.
Zazi, jailed on charges of conspiracy to use weapons of mass destruction, publicly proclaimed his innocence in recent days to anyone who asked. His plainspoken defense to The Associated Press outside his Colorado home days before his arrest: "I'm an airport driver, and that's all I can say."
Zazi "maintains that he was not part of a terrorist cell," his attorney Arthur Folsom said Friday.
But information from court papers, interviews with friends and relatives and an e-mail trail stretching from Pakistan to Colorado portray a terrorism suspect who until last year had led an unremarkable, working-class immigrant's life.
Zazi was born in Afghanistan in 1985, moving with his parents and siblings to neighboring Pakistan at age 7, his family said. At 14 — two years before the terrorist attack on the World Trade Center — he moved to America, settling in Queens to join family members who made livings as cab drivers and operators of curbside coffee stands.
He lived in a six-story, red-brick apartment building around the corner from a mosque, where friends said he was a fixture before and after leaving public high school. His classmate Naiz Khan said they played football and pool a few times there. They prayed at the mosque and worked as coffee cart vendors.
Zazi used to make fun of Khan for being "cheap," he said, and said he wasn't spending enough money.
Over a few months in early 2008, Zazi opened dozens of credit card accounts and racked up thousands of dollars in debt, according to court records, making purchases at Macy's, Radio Shack and Best Buy, among others. He filed for bankruptcy with more than $50,000 in debt in March, a couple of months after leaving the city for Denver.
He spent several months of the past year in the Peshawar region of Pakistan, where his aunt said he had a bride whom he married several years ago.
Papers filed in federal court in Brooklyn say that Zazi and unidentified associates took Qatar Airlines Flight 84 out of Newark, N.J., to Pakistan a year ago in August; while he was there, prosecutors say, he e-mailed himself handwritten notes on how to make and handle bombs.
Authorities say Zazi told the FBI in Colorado that instead of bonding with his family, he went to a training camp and learned about explosives — specifically the homemade bombs used on the mass transit attack in London in 2005 and by shoe bomber Richard Reid, who tried to destroy a trans-Atlantic flight in 2001 with explosives hidden in his shoes.
The instructions specifically noted that two key ingredients — acetone and hydrogen peroxide — were found in nail polish remover and hair salon products.
Shortly after returning from Pakistan in January, Zazi moved in with relatives in Aurora. He later moved into another Aurora home with his father and got his license to drive the airport van.
Khan said Zazi called him and happily talked about a hassle-free life, that he had no trouble finding parking.
"He was happy there," said Khan, who was questioned for hours by the FBI after Zazi stayed with him.
Between shuttling passengers to and from the airport, Zazi continued his self-education in terrorism, papers said.
He bookmarked a Web site on his computer for "lab safety for hydrochloric acid," one of three ingredients that make up triacetone triperoxide, or TATP, the explosive used in London, court papers said, and searched a beauty salon Web site for peroxide.
Zazi and at least three others scoured the Aurora shops for an unusually high number of peroxide and acetone products, prosecutors said. In July and August, the dark-haired man bought six bottles of Liquid Developer Clairoxide and several more of Ms. K Liquid 40 Volume, peroxide-based hair dye products.
On Sept. 6, Zazi took some of his products into a Colorado hotel room, outfitted with a stove on which he later left acetone residue, authorities said. He repeatedly sought another person's help cooking up the bomb, "each communication more urgent in tone than the last," the papers said.
The FBI was listening to Zazi and becoming increasingly concerned as the attacks' anniversary, and a scheduled visit by President Obama to New York, approached, officials said.
Their concern grew on Sept. 8 when Zazi got back on his computer, court papers say, located a Web site for a home improvement store in Queens and clicked repeatedly on a listing for Kleen Strip Green Safer Muriatic Acid, another name for hydrochloric acid.
Agents were tracking Zazi the next day when he rented a car and drove 1,800 miles to the city, where Khan said he met him praying at the mosque and learned he had come to fix a permit problem with his coffee cart. Zazi spent the night at Khan's house, blocks from where he grew up.
Zazi, while under heavy surveillance, was pulled over on the George Washington Bridge as he crossed from New Jersey to Manhattan and agreed to what he was told was a random drug search. Investigators who later towed Zazi's car captured his laptop's hard drive and bomb-making notes, prosecutors said.
At Khan's house, a scale that authorities said could have measured the chemicals was found with Zazi's fingerprints on it, court papers said.
The FBI was listening when Zazi told a Queens imam — a police source in the community — that his car's disappearance made him fear he was being watched. The imam later tipped Zazi off, saying police had come around and asked questions, a criminal complaint says.
"Trust me, that is a good sign," said the imam, Ahmad Wais Afzali, according to the recording. "The bad sign is for them coming to you guys and picking you up automatically."
Zazi was already back in Denver — cutting a five-day trip short and flying back on Sept. 12, after making a quick visit to old customers at the coffee cart around the corner from Wall Street, and less than a mile from the trade center site.
Three days later, he posed for pictures in his doorway in Aurora and said he wasn't a terrorist. He had spent Sept. 11 in New York City and flew back home, he said.
"And," he added, "I have nothing else to say."