Tamerlan Tsarnaev implicated in 2011 slayings

(UPI) -- Slain Boston bombing suspect Tamerlan Tsarnaev has now been tied to another incident just 16 months before the marathon attack, according to prosecutors.

Brendan Mess, known now as Tsarnaev's "only American friend," was murdered at his home in Waltham, Mass., along with housemates Raphael Teken and Erik Weissman, on the 10th anniversary of 9/11.

Their throats had been slit with a knife or ice pick, then covered with marijuana. Nearly $5,000 was found at the scene.

This finding is the first official statement that links the elder Tsarnaev to the crime, and raises questions about the death of his friend Ibragim Todashev, who died in May during an interview with authorities.

Todashev had allegedly confessed his and Tsarnaev's involvement in the murder to the FBI before he was shot after attacking one of the agents.

"According to Todashev, Tamerlan Tsarnaev participated in the Waltham triple homicide," prosecutors wrote in a motion filed on Monday.

The documents would have little effect on the trial of Dzhokhar Tsarnaev, Tamerlan's younger brother, and prosecutors say they could jeopardize the investigation into the Waltham murders.