NEW YORK (AP) — 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.”

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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.