Nafis was a terrible student in his native Bangladesh, and his middle-class parents said he persuaded them to send him to study in the U.S. as a way of improving his job prospects. They don't believe he was planning an attack.
His father, a banker, said Nafis was so timid he couldn't venture out onto the roof alone.
"My son couldn't have done it," Quazi Ahsanullah said, weeping.
"He is very gentle and devoted to his studies," he said, pointing to Nafis' time studying at the private North South University in Dhaka.
Belal Ahmed, a spokesman for the university, said Nafis was put on probation and threatened with expulsion if he didn't bring his grades up. Nafis eventually stopped coming to school, Ahmed said.
Ahsanullah said his son had argued that a U.S. degree would give him a better chance at success in Bangladesh. "I spent all my savings to send him to America," the father said.
Nafis moved to Missouri, where he studied cybersecurity at Southeast Missouri State University. He also became vice president of the school's Muslim Student Association and began attending a mosque.
But he withdrew after one semester and requested over the summer that his records be transferred to a school in Brooklyn. The university declined to identify which school.
Dow, his former classmate at Southeast Missouri State, said Nafis spoke admiringly of bin Laden. At the same time, "he told me he didn't really believe bin Laden was involved in the twin towers because he said bin Laden was a religious man, and a religious man wouldn't have done something like that," Dow said.
He said Nafis gave Dow a copy of the Quran and asked him to read it. But he "didn't rant or rave or say crazy stuff," Dow said.
"What really shocked me the most was he had specifically spoken to me about true Muslims not believing in violence," Dow said.
Dion Duncan of St. Louis, a fellow student and member of the Muslim organization, said: "Nafis was a good kid. He showed no traces of anti-Americanism, or death to America, or anything like that. He was a trustworthy, honest kid."
"He was polite and courteous. He was helpful. All the things you would expect from a good Muslim kid. He prayed five times a day," Duncan said.
Associated Press Writers David B. Caruso in New York, Jim Suhr in St. Louis, Julie Watson in San Diego, and Farid Hossain in Dhaka, Bangladesh, contributed to this report.
- Super Bowl throwback: 11 heart surgeries...
- Survivors pulled out from building 2 days...
- Debate Takeaways: Rubio shaken, Trump not...
- North Korea's new satellite flew over Super...
- Rescuers in Taiwan pull out survivors from...
- 10 Things to Know for Today: New Hampshire,...
- General Mills’ Betty Crocker, Pillsbury...
- Christie, others hit final stretch in New...
- US adds just 151k jobs in January; 4.9... 29
- Clinton seeks to cut into Sanders' New... 9
- 5 things to know about the Super Bowl... 9
- Clinton's New Hampshire challenge:... 6
- US productivity fell at sharp 3 percent... 5
- Democratic race down to just two:... 5
- Debate Takeaways: Rubio shaken, Trump... 5
- For the Clintons, New Hampshire is the... 5