Neither official was sure of the extent of Todashev's supposed involvement.
Former roommate Khusen Taramov said the FBI was asking questions about a conversation Todashev had with the older bombing suspect a month before the Boston Marathon attack.
The ex-roommate said Todashev shared the substance of his previous conversations with investigators with him and that he was completely forthcoming. That's why he was surprised that Wednesday's interview ended the way it did.
"He told them everything," Taramov said. "He told everything he knew. ... I don't know why that (the shooting) happened. It's crazy."
But Taramov also said Todashev was afraid before Wednesday's interview.
"That's what he asked me before he pretty much died," Taramov said. "He asked me, 'If something happens can you go out and tell all the truth, what exactly happened.'"
Like Todashev, the Tsarnaev brothers have roots in the turbulent Russian regions of Dagestan and Chechnya, which have become recruiting grounds for Islamic extremists. Investigators have said the brothers carried out the Boston bombing in retaliation for the U.S. wars in Iraq and Afghanistan.
An FBI team was dispatched from Washington to review the shooting, standard procedure in such cases.
Police records suggest Todashev had a hot temper. He was arrested this month on a charge of aggravated battery after getting into a fight over a parking spot with a father and son at an Orlando shopping mall. The son was hospitalized with a split lip and several teeth knocked out, according to a sheriff's report. Todashev claimed self-defense.
"By his own admission Todashev was recently a former mixed martial arts fighter," the arresting deputy said in his report. "This skill puts his fighting ability way above that of a normal person."
Todashev was released on $3,500 bail after his May 4 arrest. His attorney, Alain Rivas, didn't respond to a call for comment Wednesday.
Todashev was also arrested by Boston police in 2010 after a road rage encounter. Witnesses told police that he argued with two other drivers and cut them off with his vehicle. According to a police report, he yelled, "You say something about my mother, I will kill you."
Todashev's said he was worried that with his son was dead, the FBI could now pin any crime on him.
"Out of fear of the lawlessness in Chechnya, I sent him to the U.S., because it seemed like the safest country at the time," he said. "Now I'm thinking about how to bring home his body. As it turns out, I sent him to his death."
Associated Press writer Steve LeBlanc and AP Legal Affairs Writer Denise Lavoie in Boston; Pete Yost in Washington; Musa Sadulayev in Grozny, Russia; and Mike Schneider and Tony Winton in Orlando contributed to this report.