Three people were killed and more than 270 wounded on April 15 when two bombs exploded near the marathon’s finish line. Tamerlan Tsarnaev, 26, died after a gunfight with police days later. His 19-year-old brother was captured and lies in a prison hospital. Their mother has said the allegations against them are lies.
Investigators have not said whether the pressure cooker bombs used in the attacks were made with gunpowder extracted from fireworks.
Kadyrbayev and Tazhayakov have been in jail for more than a week on allegations they were in violation of their student visas, one because he was skipping classes, the other because he was no longer enrolled. All three men charged Wednesday began attending UMass with Tsarnaev in 2011, according to the FBI.
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.
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 noticed a backpack containing fireworks, which had been opened and emptied of gunpowder, the FBI said. 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.”