A friend of Boston bombing suspect Tamerlan Tsarnaev implicated himself and Tsarnaev in an unsolved triple homicide before authorities say he instigated a violent confrontation that resulted in his death early Wednesday morning, CBS News correspondent Bob Orr reports.

Law enforcement sources told Orr that the man, a Chechen identified as Ibragim Todashev, implicated himself and Tsarnaev to authorities in the 2011 killings in Waltham, Mass., under questioning Wednesday at Todashev's apartment in Orlando, Fla.

Authorities went to the apartment after having obtained what the sources described as strong evidence to suggest that Todashev, Tsarnaev and his brother Dzhokhar were involved in the killings on the tenth anniversary of the Sept. 11, 2001, terror attacks.

The sources also said that authorities have no evidence tying Todashev to last month's deadly terrorist bombing at the Boston Marathon that the Tsarnaev brothers are accused of carrying out.

Sometime after midnight Wednesday morning in Orlando, an FBI special agent from the bureau's Boston field office was accompanied by at least two troopers from the Massachusetts State Police and a Joint Terrorism Task Force agent to question Todashev, the sources said. The questioning primarily focused on the 2011 killings.

While the FBI's investigation into Wednesday's shooting is ongoing, the preliminary details are that after Todashev implicated himself and Tamerlan Tsarnaev he became angered when authorities pressed him for a full confession, the sources said. Todashev brandished a knife, prompting the officials to feel that their lives were in danger. The FBI agent then shot Todashev.

The Tsarnaev brothers and Todashev apparently knew the three people killed in Waltham, the sources said.

The sources described the 2011 killings as brutal and grisly, with all three bodies nearly decapitated. The bodies had marijuana and thousands of dollars in cash sprinkled on them.

Todashev lived in the Boston area at the time of the killings and was friends with Tamerlan Tsarnaev, who died in a shootout with authorities in the days after the April 15 attack. It's unclear what kind of a relationship Todashev had with Dzhokhar Tsarnaev, who remains in federal custody awaiting trial.