Both officials spoke on condition of anonymity because they were not authorized to discuss the investigation publicly.
On Capitol Hill, members of the Senate Intelligence Committee were briefed by the FBI and other law enforcement officials at a closed-door session last night.
Afterward, Sen. Marco Rubio, R-Fla., described the two brothers as “a couple of individuals who become radicalized using Internet sources.”
“So we need to be prepared for Boston-type attacks, not just 9/11-style attacks,” Rubio said, referring to lone-wolf terrorists as opposed to well-organized teams from established terror networks.
Sen. Saxby Chambliss, R-Ga., said law enforcement officials have gotten “minimal” information from Dzhokhar Tsarnaev and are still looking into whether the brothers had training or coaching from a foreign group.
The brothers’ parents live in Dagestan, a predominantly Muslim province in Russia’s Caucasus, where Islamic militants have waged an insurgency against Russian security forces for years.
Family members reached in the U.S. and abroad by The Associated Press said Tamerlan was steered toward a strict strain of Islam under the influence of a Muslim convert known to the Tsarnaev family only as Misha.
After befriending Misha, Tamerlan gave up boxing, stopped studying music and began opposing the wars in Afghanistan and Iraq, according to family members, who said he turned to websites and literature claiming that the CIA was behind 9/11.
“Somehow, he just took his brain,” said Tamerlan’s uncle, Ruslan Tsarni of Montgomery Village, Md., who recalled conversations with Tamerlan’s worried father about Misha’s influence.
“You could always hear his younger brother and sisters say, ‘Tamerlan said this,’ and ‘Tamerlan said that.’ Dzhokhar loved him. He would do whatever Tamerlan would say,” recalled Elmirza Khozhugov, the ex-husband of Tamerlan’s sister. He spoke by telephone from his home in Almaty, Kazakhstan.