Dead Massachusetts bombing suspect implicated in 2011 killings , official says . Another man , FBI Todashev , attacks Ibragim agent with a knife , is killed . Both men were members of the mixed martial arts forum Sherdog.com , along with Russian-Canadian boxer-turned-jihadist William Plotnikov , the source said . Todashev had admitted to a role in a 2011 triple murder in Chechnya . Authorities told him not to take a pending flight to Massachusetts .
Dead Massachusetts bombing suspect implicated in 2011 killings , official says . Another man , FBI Todashev , attacks Ibragim agent with a knife , is killed . Todashev had admitted to a role in a 2011 triple murder in Chechnya . Authorities told him not to take a pending flight to Massachusetts .