
Ok so he killed 8 people and was Interrogated by police I kinda think that the officer is actually Jaeha and Yosoeb killed 8 people so he could meet him again or something

Not a spoiler reread the beginning of chapter 13.
http://www.mangago.zone/read-manga/an_uncomfortable_truth/mf/c013/3/
he is in the police office alive.
I think they all deserve to suffer but Donghyuk he's just traumatized and as for Kyungsoo he broke his heart so bad it's just my opinion though