Khairullozhon Matanov, 23, of Quincy, was arrested at his apartment shortly after 5 a.m. by FBI agents, with the help of Quincy police officers, police Capt. John Dougan said. He was booked at the Quincy Police Department before being brought to Boston for his arraignment Friday afternoon in U.S. District Court.
Matanov destroyed, altered and falsified records in a federal investigation, and made false statements in a federal investigation, federal prosecutors said. A legal resident of the U.S. originally from Kyrgyzstan, Matanov is not accused of participating in the bombings or of knowing about them in advance.
"This is the most significant information that has come out on this incident since the initial arrests," said former Boston Police Commissioner and current WBZ-TV security analyst Ed Davis.
Matanov's lawyer, Paul Glickman, did not immediately return a phone message left Friday morning at his office. Matanov's phone number could not immediately be located.
Matanov knew Tamerlan and Dzhokhar Tsarnaev, and in the days after the April 2013 bombings that killed three people and injured more than 260, Matanov realized the FBI would want to talk with him because he shared their "philosophical justification for violence," prosecutors said.
He talked to the brothers on numerous occasions after the bombings, and even took them out to dinner the day of the explosions, they said.
"In the days following the bombings, Matanov continued to express support for the bombings, although later that week he said that maybe the bombings were wrong," the indictment said.
He tried to contact the brothers after he saw media reports identifying them as the suspects, prosecutors said.
Matanov deleted information regarding the brothers from his computer, including Internet searches, they said.
He also allegedly asked a friend to destroy his cellphones, but that friend refused.
And he repeatedly lied to investigators about the extent of his friendship with the Tsarnaev brothers, prosecutors said.
The brothers, ethnic Chechens who lived in the former Soviet republic of Kyrgyzstan and the Dagestan region of Russia, settled in the United States more than a decade ago.
Dzhokhar Tsarnaev, 20, has pleaded not guilty to several federal charges and is awaiting trial. Prosecutors allege he and his brother planted two pressure cooker bombs near the marathon's finish line. Tamerlan Tsarnaev, 26, was killed during a gunbattle with police four days after the bombings.
The Associated Press contributed to this report.