( CNN ) -- The slaying of one of Tamerlan Tsarnaev 's best friends in September 2011 is now being reviewed by a `` wider group of eyes , '' a source close to the Boston bombing investigation tells CNN . The killings of Brendan Mess and two others -- all of whom had their throats slit -- in Waltham , Massachusetts , remain unsolved . The Middlesex County district attorney 's office said at the time that the three victims were killed by `` sharp force injuries of the neck . '' District Attorney Gerry Leone said days after the crime that the victims and two unknown perpetrators appeared to know each other and that it was not a random crime . No suspects were named or arrests made in the case . Tsarnaev and Mess were sparring partners at a local gym , and the source tells CNN investigators believe he was one of the last people to see Mess alive . Aunt reveals clue to Tamerlan 's trip to Russia . Investigators of the crime reported at the time that the heads of the three victims were pulled back and their throats slit ear to ear with great force . Marijuana was spread over the bodies in a `` symbolic gesture , '' and several thousand dollars in cash was found at the scene . On Monday , Middlesex County District Attorney 's spokeswoman Mary Beth Long told CNN , `` We will review any new information that may come to light in ( the triple homicide ) as a result of the investigation into alleged marathon bombing suspect Tamarlen Tsarnaev . '' Long said the case has always been an open investigation and that they continue to follow all leads . A sister of one of the victims told CNN that she has been recently contacted by investigators in the case . `` She 's meeting with them next week , '' said CNN 's Ashleigh Banfield . `` Investigators on that case are meeting with her and have been speaking with her since Saturday . Not only that , she confirms to me that the same detectives are still on that case and that they are detectives that she has spoken with in the past . '' Uncle : Cambridge friend 'brainwashed him completely ' The sister , who requested to remain anonymous , said investigators have been very interested in trying to determine if there is any relationship between her brother and Tsarnaev , Banfield said . `` She could n't really enlighten these detectives at all because she felt her brother was n't a friend or acquaintance at all of Tamerlan Tsarnaev , '' Banfield said . But the sister said she hopes the new interest will lead to her brother 's case being solved .
' Tsarnaev 's friend and sparring partner was killed in action . The friend , Brendan Mess , and two others had their throats slit . Note : The crime is being reviewed by ` ` wider set of experts ''