( CNN ) -- The FBI was expected Thursday to seize the original hard drives from the surveillance system at Lowndes High School , where 17-year-old Kendrick Johnson was found dead in a rolled-up gym mat earlier this year , according to a source with knowledge of the investigation surrounding the hard drives . U.S. Attorney for the Middle District of Georgia Michael Moore issued a grand jury subpoena to seize the hard drives , the source said . Kendrick Johnson 's family waited months for hundreds of hours of surveillance video , hoping it would yield answers about their son 's January death , but they were disappointed to learn that the four cameras inside the Valdosta , Georgia , gymnasium showed only a few collective seconds of Johnson , jogging . The camera fixed on the gym mats was blurry . The Johnsons ' attorneys were not shy in stating their suspicion that someone could have tampered with the videos . Attorney Chevene King has questioned why time codes were n't shown in the videos . `` We do n't have any time code with which to synchronize the events that are shown in the video . ... Either the cameras did this on their own or a human being interacted to make these cameras do these things , '' King said . Lowndes County Schools insisted last month that the video it provided to the family and CNN is `` a raw feed with no edits , '' and the county sheriff 's office , which asserts Johnson accidentally died while reaching for a shoe in one of the mats , says it did n't edit any files , according to their lawyers . CNN , which filed suit to secure access to the video , hired forensic video analyst Grant Fredericks to analyze more than 290 hours of material from all 35 cameras inside and outside of the gym . Fredericks is a U.S. Justice Department consultant and contract instructor for the FBI National Academy in Quantico , Virginia . Kendrick Johnson 's family holds rally after filing complaint about missing organs . CNN also provided Fredericks and his company , the Spokane , Washington-based Forensic Video Solutions , with hundreds more hours of video from 31 cameras in other parts of Lowndes High School . Fredericks quickly knocked down most of the Johnsons ' concerns -- they 're all easily explained , he said -- but his examination raised what could be another mystery : at least an hour of missing video from all four cameras inside the gym . Fredericks told CNN he found that `` highly suspicious , '' especially considering how the material was acquired by police . CNN has requested access to the original surveillance servers , which has not yet been granted . But Fredericks cautioned that the video could be gone , as newer surveillance would replace it if it was n't recovered promptly from the school 's digital video recorder . The files given to him by CNN are not original , Fredericks has said . `` They 're not something investigators should rely on for the truth of the video . '' The analyst added : `` The investigator 's responsibility is to acquire the entire digital video recording system and have their staff define what they want to obtain . '' Coroner slams handling of Kendrick Johnson case . Authorities have said they did n't receive a copy of the videos until several days after Johnson 's body was found , according to an unredacted report obtained by CNN after a legal process . According to an incident report from the sheriff 's office , a detective watched a portion of the video , then asked an information technology officer employed by the school board to produce a `` copy of the surveillance video for the entire wing of the school with the old gym for the last 48 hours . '' Five days later , the sheriff 's report says , the IT officer delivered a hard drive to the detective , who verified it contained what he requested . `` Right now , what they 've done , is they 've left it up to the school district as to what it is they want to provide to the police , and I think that probably is a mistake , '' Fredericks said . `` You do n't want somebody who might be party to the responsibility to make the decision as to what they provide the police . '' Jacquelyn Johnson , Kendrick Johnson 's mother , said of the case , `` We 're going to fight until it 's all over , until we get the truth . '' Federal prosecutor will look into Kendrick Johnson case . CNN 's Devon Sayers contributed to this report , which was written by Eliott C. McLaughlin .
January : District attorney issues grand jury warrant for school hard drives . Kendrick Johnson 's body was found in a rolled - up gym mat in January . Previously released footage was missing footage from high school gym . Forensic video analyst : Hard drives may have been overwritten by now .