
wait wat.... sorry i'm confused, so does he have evidence that sangwoo killed Chief Kwak?

Sadly, they have no evidence right now. Listening to that recording, however, seems to be what Seungbae needed to get his shit together. I'm adding a link below to a previous post I made about the recording if you'd like to see my thoughts. Hopefully it helps!
http://www.mangago.zone/home/mangatopic/3707679/
*flips table* NEED MOREEE