QUINCY — At the mosque where he worshiped each Friday, Khairullozhon Matanov was seen as an unassuming, affable young man, a hard-working cab driver trying to make his way in a new country. He played in a weekly soccer league, wore blue jeans and T-shirts.
Nothing about him, several members of the mosque said, seemed at all extreme.
But at the brick apartment complex where the 23-year-old lived, some neighbors saw Matanov in a more mysterious, even menacing light. He never spoke to anyone, and walked with his head down, avoiding eye contact even when people said hello. Looking down into his basement apartment, neighbors saw that he slept on a mattress on the floor.
“He kind of scared me,” said Leslie Aiello, 49.
About 5:30 Friday morning, Aiello and other neighbors woke up to find their building surrounded by a SWAT team and some 30 FBI agents, who took Matanov into custody on charges of obstructing the investigation into the Boston Marathon bombings.
Neighbors said they had noticed an intermittent police presence outside the apartment over the past year, particularly around the anniversary of the bombings. Some suspected that Matanov was the target of the surveillance.
Yet Monday’s disclosure that Matanov had been friends with the bombing suspects and may have shared their radical beliefs left many who knew him stunned and deeply shaken.
“I had no clue he was this closely tied to them,” said neighbor Tyler Young, 27. “It’s shocking. I didn’t understand the gravity of the whole thing.”
To cabdrivers in Braintree, where Matanov had worked for more than two years, his friendship with the bombing suspects was no secret.
His boss at Braintree Checker Cab said Matanov revealed to colleagues that he knew the Tsarnaev brothers in the days after they had been identified as the bombing suspects and was “adamant they didn’t do it.”
“Not those guys — they got it wrong, or they are being framed,” the company owner recalled Matanov saying. “They would never have done that.”
The owner, who asked to be identified only by his first name, Nour, said Matanov made no secret of his friendship with the suspects. But with the shock of the bombings still raw, drivers asked few questions.
“When it just happened, nobody wanted to talk about it,’’ Nour said. “It was cut short. And nobody probed any further, so he didn’t say anything else.”
Matanov said he had met the Tsarnaevs while playing soccer, Nour said.
At the cabstand in Braintree, drivers who knew Matanov described him as a likeable, regular guy who showed no signs of extremist tendencies.
“That would be a surprise,” said Jerome Shea, a Checker Cab driver. “He’s a real nice guy, hard-working kid. He’s always been pleasant to me.”
Matanov, who is a native of Kyrgyzstan and had no family in the United States, came here on a student visa in 2010, his lawyer, Edward Hayden, said in court.
He studied information technology at Quincy College, but discontinued college at some point. Hayden said he believed it was because of financial problems.
Matanov then applied for asylum and was granted it because of turmoil in Kyrgyzstan.
Matanov comes from Suzak, a small town on Kyrgyzstan’s border with Uzbekistan in the volatile Fergana Valley region of the former Soviet Union. The area was riven with violence between ethnic Kyrgyz and ethnic Uzbeks that took hundreds of lives in 2010, the year Matanov came to the United States. The Fergana Valley has a large population of devout Muslims and has been a fertile recruiting ground for Islamic militants since the breakup of the Soviet Union.
The Tsarnaev family emigrated from a different part of Kyrgyzstan in the early 2000s.
Matanov has four brothers, two in Kyrgyzstan, two in Russia, Hayden said. His mother is very ill with diabetes and his father had a stroke and is partially paralyzed, the lawyer said.
Matanov was a reliable presence at Friday services at the Islamic Center of New England’s Quincy mosque and played soccer with members in Cohasset, said Ahmed Goutay, who organized the team.
Goutay said FBI agents had questioned him about Matanov in the weeks after the bombings. When he told Matanov that he had been interviewed, Matanov said he was not involved. “He said he had nothing to do with it,’’ Goutay said.
As time passed and Matanov was not arrested, Goutay and others assumed the questioning was just a formality.
“If he is not in prison, he must be innocent,” he said.
Matanov never discussed his feelings about the bombings, terrorism, or Islamic fundamentalism, said Goutay, who was surprised by the arrest and the allegations.
Nour said he believed that Matanov also attended services in Cambridge and Sharon, when his job took him there at the time of services.
Administrators at the Islamic Society of Boston’s Cambridge mosque attempted Friday to determine if Matanov was the same Russian-sounding young man who occasionally sat with Tamerlan in the rear of the mosque during Friday services.
Ismail Fenni — acting imam of the mosque, which Tamerlan attended occasionally with his brother — said Tamerlan once introduced him to a friend who appeared to speak the same language and to be of similar descent.
Fenni said that the man attended the mosque several times after the Marathon bombing but has not shown up lately.
The mosque has no record of Matanov’s name, Fenni said. But he added that many who attend do not register their names.
Nour said that when Matanov began working for him about two years ago, the young man would avoid looking at attractive women as they walked by, but that more recently he changed his ways.
“He was a little bit more observant at the beginning; he would not look at a girl . . . walking by,’’ Nour recalled. “But lately, he’s a little bit more open to the average 23-year-old’s behavior.’’
Nour said he never observed Matanov listening to recorded sermons from imams, but instead listened to standard radio stations, especially while working as a cabdriver.
Nour said Matanov dressed like any other person in their 20s and would usually wear jeans, sneakers, and a shirt. “He wasn’t dressed in, like, a radical way, or in any odd way,’’ Nour said. “He was dressed the same way that the majority of people would dress.’’
Nour said that if Matanov is found not guilty of the charges he faces, he would readily hire him back.
“If the law proves he didn’t do it, then, yeah, I would definitely offer him a job,’’ Nour said. “He’s a go-getter. He would go and get it done.’’
to this report. Peter Schworm can be reached at schworm@
globe.com. Follow him on Twitter @globepete.