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The Lowell Sun, Julia Malakie / AP Tamerlan Tsarnaev

Tamerlan Tsarnaev, the Boston Marathon bombing suspect who was killed in a shootout with police in April, was named as a participant in a 2011 triple homicide, according to new court filings this week.

Federal prosecutors building the case against Tsarnaev’s younger brother Dzhokhar filed documents on Monday that detail Tamerlan’s role in the triple murder in September 2011, where three men were found in an apartment in Waltham, Mass. with their necks slit and their bodies covered with marijuana. According to the filing, Ibragim Todashev told investigators that Tamerlan participated in the killings. Todashev was shot and killed by the FBI in May when authorities said he turned violent during questioning in his Orlando home.

Dzhokhar Tsarnaev, the surviving bombing suspect, faces 30 federal charges, including using a weapon of mass destruction, and could face the death penalty.