Updated

The parents of a Georgia teenager found dead at school inside a rolled-up gym mat still have unanswered questions after officials released hours of surveillance camera footage in the case.

The body of 17-year-old Kendrick Johnson of Valdosta was found Jan. 11, and sheriff's investigators concluded he died in a freak accident. Johnson's parents insist someone must have killed him.

At a news conference Thursday, Johnson family attorney Chevene King Jr. said a lack of time codes and blurry footage from the gym where Johnson was found dead make him question the credibility of the surveillance footage released this week.

Jim Elliott, the attorney for the Lowndes County sheriff, has said surveillance cameras at the school did not capture the circumstances that led to Johnson's death.