My intuition told me that the victim was killed in a hurry because he might reveal the murderer’s identity. Since the two were old classmates, the murderer had no trouble at all approaching the victim. 

However, this was merely speculation, so I kept it to myself.

"Song Yang-gege, look at the victim’s skin!" blurted Bingxin.

There were tiny wounds all over the victim’s skin that had turned white. I also caught a whiff of bleach. Upon further examination, I said, "The murderer scalded the victim with boiling water and scrubbed him clean with a steel mesh, making sure all his fingerprints were removed."

"How can he do this to his own classmate! He must be the devil!" cursed Bingxin. 

Like the previous victims, his face was disfigured by hydrochloric...