Tazhayakov was allowed to return to the U.S. from Kazakhstan in January despite not having a valid student visa, a federal law enforcement official told The Associated Press. His student visa status had been terminated because he was academically dismissed from the university, said the official, who was not authorized to discuss the case and spoke on condition of anonymity.
All three men charged Wednesday began attending UMass with Tsarnaev in 2011, according to the FBI.
Kadyrbayev, an engineering major, said he and Tazhayakov hung out with Tsarnaev on and off campus. The three often spoke Russian among themselves.
He told authorities he became "better friends" with Tsarnaev, an ethnic Chechen, in spring 2012, and that he was a frequent visitor to the Tsarnaev home in Cambridge.
The FBI said that before Tsarnaev's roommate let the three friends into the room, Kadyrbayev received a text message from Tsarnaev that read: "I'm about to leave if you need something in my room take it," according to the FBI. When Tazhayakov learned of the message, "he believed he would never see Tsarnaev alive again," the FBI said in the affidavit.
It was unclear from the court papers whether authorities believe that was an instruction from Tsarnaev to destroy evidence.
Once inside Tsarnaev's room, the men watched a movie. At some point, they noticed a backpack containing more than a half-dozen fireworks, each about 8 inches long, according to the affidavit. The black powder had been scooped out.
The FBI said that Kadyrbayev knew when he saw the fireworks that Tsarnaev was involved in the bombings and decided to remove the backpack "to help his friend Tsarnaev avoid trouble."
Kadyrbayev also decided to remove Tsarnaev's laptop "because he did not want Tsarnaev's roommate to think he was stealing or behaving suspiciously by just taking the backpack," the FBI said.
After the three returned to Kadyrbayev's and Tazhayakov's apartment with the backpack and computer, they watched news reports featuring photographs of Tsarnaev. The FBI said Kadyrbayev told authorities the three men then "collectively decided to throw the backpack and fireworks into the trash because they did not want Tsarnaev to get into trouble."
Kadyrbayev said he placed the backpack and fireworks along with trash from the apartment into a large trash bag and threw it into a garbage bin near the men's apartment, according to court papers.
When the backpack was later found, inside it was a UMass-Dartmouth homework assignment sheet from a class Tsarnaev was taking, the FBI said.
The court papers do not say what happened to the laptop.
In a footnote, the FBI said: "Tazhayakov also informed the FBI agents that while eating a meal with Dzhokhar and Kadyrbayev approximately one month prior to the marathon bombing, Dzhokhar had explained to Kadyrbayev and Tazhayakov that he knew how to make a bomb."
Robert Stahl, an attorney for Kadyrbayev, said his client "absolutely denies the charges" and didn't know that the backpack and fireworks were part of the bombing case. Kadyrbayev is "just as shocked and horrified by the violence in Boston that took place as the rest of the community is," the lawyer said.
He also denied that Kadyrbayev instantly recognized Tsarnaev's photo and said Kadyrbayev didn't know Tsarnaev was involved in the bombing: "His first inkling came much later," he said.
Tazhayakov's lawyer, Harlan Protass, said Tazhayakov "feels horrible and was shocked to hear that someone he knew at the University of Massachusetts Dartmouth was involved with the Boston Marathon bombing."
Kadyrbayev and Tazhayakov lived at an off-campus apartment in New Bedford, about 60 miles south of Boston, and got around in a car registered to Kadyrbayev with a souvenir plate that read "Terrorista (hash)1." The car was pictured on Tsarnaev's Twitter feed in March.
The plate was a gag gift from some of Kadyrbayev's friends, meant to invoke his penchant for late-night partying rather than his political sentiments, Kadyrbayev's lawyer said last week.
Breed reported from Raleigh, N.C. Contributing to this report were Associated Press writers Bridget Murphy and Rodrique Ngowi in Boston and Michelle R. Smith in Providence, R.I.
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