Who kills Shido?

Could you elaborate on the mystery surrounding the death of Shido? Who is the perpetrator of this tragic event? Is there any evidence pointing towards a particular suspect? Have the authorities launched an investigation into the matter, and if so, what are the current leads? Additionally, have there been any rumors or theories circulating among the public regarding the identity of the killer? This case certainly seems intriguing, and I'm eager to learn more about it.