An acquaintance of deceased Boston Marathon bombing suspect Tamerlan Tsarnaev was "about to sign a statement" confessing his and Tsarnaev's involvement in an unsolved triple murder when he was killed by an FBI agent, sources told ABC.
Ibragim Todashev, 27, was questioned Wednesday in Orlando, Fla. about his connections to the older of the two bombing suspects, whom he knew through their participation in Mixed Martial Arts.
At some point during the interview, Todashev "just went crazy," law enforcement officials told ABC News. The Chechen immigrant pulled out a knife and stabbed the FBI agent several times before the agent shot and killed him. The agent's injuries were non-life threatening.
CBS News correspondent Bob Orr reports that prior to the attack, Todashev implicated himself and Tamerlan Tsarnaev in the murder of three Massachusetts men in 2011. Brandon Mess -- Tsarnaev's former roommate -- and two others were slain in Mess' apartment, their throats slashed and bodies covered in marijuana.
Sources with "direct knowledge of the case" told ABC News that Todashev was "about to sign a statement" confessing that he and Tsarnaev had been involved in the killings.
According to CBS, officials have no evidence tying Todashev to the Boston Marathon bombings, which left three dead and more than 200 injured.