Same. Actually, I didn't even realize they didn't show how the murder was committed, you made a good observation. They haunted HS so much but did the minimum with the actual murderer.
I was also expecting them to show what path he will choose. I was thinking he will become a lawyer to save others too. Kinda sad that they didn't show him in the future. Also, they left a lot of places for interpretation. It really gave me chills when he went to his room and it looked so lifeful while he was dead inside. He had to grow up overnight. The scene on the building gave me a lot of questions - for a moment when they showed the police cars I was thinking that he committed a crime to go back to prison since he looked for CCTV in the convenience store. I also hoped he will not give up and jump.... so many questions.
