According to the records, this was what happened on the day of the crime:
The murderer entered Yu Zhigen’s house that night, brutally killed Yu Zhigen, and left his body on the couch. After killing him, the murderer tore a piece of cloth off of the couch and wrote on the wall using the victim’s blood. He splattered blood everywhere and created an extremely bloody scene before shutting the door and disappearing into the stormy night.
The neighbors had not heard anything, yielding three possible explanations: One, the murderer had closed the door; two, the storm outside was very loud; three, Yu Zhigen might have been fatally stabbed the first time and did not make any noise.