FOX UNDERCOVER - Tamerlan Tsarnaev "participated" in a brutal Waltham triple murder that left one of his friends dead, according to newly-filed court records that attribute the information to the Boston Marathon bombing suspect's now-dead friend. 
 
 The disclosure, made by federal prosecutors in the terror case against Tsarnaev's younger brother, is the first official statement linking the now-dead elder Tsarnaev to the Waltham murders for which he has long been suspected. 
 
 "(A)ccording to (Tsarnaev's friend Ibragim) Todashev, Tamerlan Tsarnaev participated in the Waltham triple homicide," prosecutors wrote in a motion filed on Monday. 
 
 The motion is part of an effort by prosecutors to block efforts by the defense team for Dzhokhar Tsarnaev to force the government to turn over every document they have concerning the Waltham triple murders. While the Waltham murders would appear to have little to do with the charges the younger Tsarnaev brother is facing, it's clear from court records that defense attorneys want the information to help fight against a possible recommendation to seek the death penalty. 
 
 Prosecutors say turning over the documents would be of little value now to the younger Tsarnaev's case and it could jeopardize the Middlesex District Attorney's ongoing and "active" investigation into the Waltham murders. A judge has yet to rule on the request. 
 
 Little has been said officially about the Waltham murders since the terror suspect's possible role first surfaced soon after his death. 
 
 Tamerlan Tsarnaev was friends with one of the victims, all of whom were killed on Sept. 11, 2011. More questions surfaced after Todashev, a fellow Chechen and friend of Tamerlan, was shot and killed by an FBI agent this past May in Todashev's Orlando apartment. 
 
 Unconfirmed media reports said that Todashev had implicated either himself, Tamerlan or both of them in the murders before reportedly turning on the FBI and Mass. State Police who were interviewing him. Todashev was shot and killed. 
 
 Todashev's father is seeking answers about the killing. An attorney he has hired, Barry Cohen of Tampa, told FOX Undercover he doesn't know what Todashev told authorities and he doesn't know who committed the Waltham murders. 

 At some point before he was shot to death in a confrontation with the FBI, Ibragim Todashev tied his buddy Tamerlan Tsarnaev’s to a triple murder in Waltham, according to papers filed in U.S. District Court in Boston. 
 
 “According to Todashev, Tamerlan Tsarnaev participated in the Waltham triple homicide,” reads a motion filed by federal prosecutors.
– Before he was killed by the FBI in a bizarre incident, Ibragim Todashev told agents that his friend Tamerlan Tsarnaev was indeed linked to a 2011 triple murder, according to papers filed by federal prosecutors in a Boston court on Monday. "According to Todashev, Tamerlan Tsarnaev participated in the Waltham triple homicide," the motion reads. Authorities have been investigating Tsarnaev's connection to the killings for a while, and various media outlets reported in May that just before he was killed, Todashev had admitted to helping Tsarnaev kill the men. But this is the first official statement connecting Tsarnaev to the triple murder, MyFox Boston reports. The motion was filed because prosecutors want to block Dzhokhar Tsarnaev's lawyers from getting documents related to Tamerlan's alleged role in the murders, the Boston Herald reports. "Disclosure of the details of that investigation could jeopardize it," the filing reads. MyFoxBoston points out that "it's clear from court records" that the defense would like to incorporate the information into the case it's likely making against the death penalty for Dzhokhar. Click for background on the horrific murders.