(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.
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Tamerlan Tsarnaev's friend and sparring partner was killed in 2011
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The friend, Brendan Mess, and two others had their throats slit
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Source: The crime is being reviewed by "wider group of eyes"
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 @placeholder, Banfield said.