Kenji Sawamura, the head of the education board, said Thursday he believes bullying was the primary cause of a 13-year-old boy's suicide, The Yomiuri Shimbun reported.
Police said the boy, who was unidentified, jumped to his death on Oct. 11 from his family's condominium. Police said on Sept. 29 multiple students allegedly covered the boy's mouth with tape and tied his arms and legs with headbands.
Police investigated at the school and education board Wednesday night and seized 129 pieces of evidence. Police said they plan to question more than 100 people regarding the suicide.