Tamerlan Tsarnaev, the older of the two Tsarnaev siblings suspected of carrying out the twin bombings during the Boston Marathon in April, was involved in a triple homicide in the neighboring town of Waltham, Mass., media reports said, citing a filing made by federal prosecutors.

Tsarnaev’s participation in the stabbing murders of three men in a Waltham apartment in September 2011 was revealed by his friend, Ibragim Todashev, during questioning by federal agents, reports said.

The three men, one of whom was a friend of Tamerlan, were found with their necks slit and their bodies reportedly covered with marijuana, the Associated Press reported. And, Todashev himself was fatally shot in his Orlando home by an interrogating official in May, after he turned violent during questioning by an FBI agent and two Massachusetts state troopers.

The filing is the prosecutors' attempt to block the younger sibling, Dzhokhar -- who is being prosecuted for charges related to the Boston bombings -- from getting access to official information, including investigative documents associated with the Waltham murders, AP reported.

Authorities contend that 20-year-old Dzhokhar and Tamerlan, 26, planned and carried out the two bombings near the Boston Marathon finish line on April 15, claiming the lives of three people and injuring more than 260 people.

The younger Tsarnaev's lawyers want the government to share with them investigative materials pertaining to the deceased Tamerlan, who was killed in a shootout with the police after a days-long manhunt following the bombings.

"The government has already disclosed to Tsarnaev that, according to Todashev, Tamerlan Tsarnaev participated in the Waltham triple homicide," prosecutors wrote.