The federal government remembers
[...] Johnson's body was found in a rolled-up mat in the Lowndes High School gymnasium on January 11, 2013. Investigators with the Lowndes County Sheriff's Office ruled his death accidental, concluding that Johnson climbed into the center of the gym mat to reach for a shoe and got stuck.
State officials later concurred that Johnson's death was accidental and listed his cause of death as "positional asphyxia," or suffocation by his own body weight. [...]
Feds subpoena Kendrick Johnson's schoolmates amid teen's death probe - CNN.com