Atlanta ( CNN ) -- The Lowndes County , Georgia , Sheriff 's Office does not believe an anonymous e-mail claiming that a former schoolmate confessed to killing Kendrick Johnson is credible , an attorney for the department told CNN on Thursday . The attorney did not tell CNN why or how investigators determined the tip was not credible . The determination was made after a Lowndes County assistant district attorney issued a grand jury subpoena to obtain identifying information about the sender of the e-mail . CNN obtained the e-mail and the subpoena Monday , in response to a state Open Records Act request submitted to the Lowndes County Sheriff 's Office . The anonymous e-mail tip is dated January 27 , 2014 . The sender of the e-mail does not suggest he or she witnessed a confession ; instead , the sender claims to have been told information by somebody who purportedly was aware of a confession in the 2013 death by one of the people implicated in the e-mail . Johnson 's body was found in a rolled-up mat in the Lowndes High School gymnasium on January 11 , 2013 . Investigators with the Sheriff 's Office ruled his death accidental , concluding that he climbed into the center of the gym mat to reach for a shoe and got stuck . According to an incident report provided to CNN by the Sheriff 's Office , investigators interviewed two of four students identified by name in the anonymous e-mail on January 28 . Both students acknowledged they knew Johnson but denied any involvement in his death . The incident report does not indicate whether the investigators attempted to speak with the two other students identified in the e-mail . CNN is not naming the students mentioned in the e-mail because none of them has been named a suspect in the death of Johnson . Lowndes County sheriff 's investigators concluded that Johnson , 17 , got stuck while reaching for a shoe at the center of the mat and that his death was accidental . The state 's medical examiner agreed , citing `` positional asphyxia '' as the cause of death . Kenneth and Jacquelyn Johnson believe their son was beaten to death and officials are `` covering up a murder . '' An independent pathologist , hired by the parents , concluded that the death was the result of a homicide after finding evidence of `` unexplained apparent non-accidental blunt force trauma '' to Johnson 's neck . `` If anybody has any information of a different opinion that they can provide to us , we 're certainly open to looking at that . We 're not closed-minded on this , '' Lt. Stryde Jones , supervisor of the Lowndes County Sheriff 's Office 's Investigative Division , told CNN in May . The Sheriff 's Office has received many public comments regarding Johnson 's death since it closed its case on May 2 . The grand jury subpoena is the first document provided to CNN that suggests the department has acted on any of those public comments . `` Although our case has been closed , if evidence comes forward , specifically testimony , then we 're open to hearing that and certainly we 'll act accordingly , '' Jones said . Chief Assistant District Attorney Bradfield Shealy issued the subpoena to Mediacom Communications Corp. on January 28 . The New York-based cable , phone and Internet provider was ordered to provide the Lowndes County grand jury with subscriber information associated with the e-mail sent through the Lowndes County Sheriff 's Office 's website , or submit the documents to the district attorney 's office or Jones before February 26 . According to a Lowndes County Sheriff 's Office incident report , the subpoena was faxed to Mediacom on February 7 . Mediacom received the subpoena via fax Wednesday afternoon and immediately complied with Georgia officials ' request , spokesman Tom Larson told CNN on Thursday . Last week , students from Lowndes High School and nearby Valdosta High School were among those who appeared before a federal grand jury in Macon , as part of the Department of Justice 's investigation into Johnson 's death . The U.S. attorney for the Middle District of Georgia , Michael Moore , launched the federal investigation on October 31 .
The Lowndes County , The Lowndes County , the Lowndes County Sheriff 's Office says it does not believe an anonymous e-mail . The e-mail claimed that a former schoolmate confessed to killing Kenneth , more than a year ago . Johnson 's body was found in a rolled-up mat in his high school gym 17 . The death was ruled an accident , but an independent pathologist called it a homicide .