I was thinking the same thing, but i wasn't too sure ╮(￣▽￣)╭
im pretty sure near the beginning of the story they said both his parents died, and the officers first suspicion was that he killed his PARENTS. plural, so i just envisioned from the start he killed both his mom and dad
thought that too at first, but then we got to see how he lived with his parents, so i just ended up thinking that just maybe the dad was the one who killed the mom and sangwoo killed the dad but oh well, will be interesting to see his reason for killing his parents
this chapter completely slammed the though i had that maybe sangwoo only killed his dad because the dad might have killed the mom D: