It's not a "maybe". He killed her, but apparently the one who killed his father was his mother.
He has oedipus complex, but his trastorned relationship with her mother makes him lover her and hate her. That's probably why she killed the other girls too. He was prob trying to love/kill her mother again and again.
With Bum is different. He looks like her so He feels the same, but it's at the same time different. He wants to hurt him, He wants to be loved by him, He feels sickened yet attracted. But He stopped himself to kill him, This is relatad to the fact that Bum is a guy. But It's about the stalking side of Bum too.
Bum is utterly damaged like him and loves him no matter what. So He looks like her mom, but is essentialy different. That's why this is so complicated.
Uhm...eh.. I think Sangwoo really hate all the woman in this manhua because they end up being killed or bullied maybe sangwoo killed her mother. He really likes bum though coz his a guy?