Can someone tell me how and why sangwoo kill his parents? It seems like I missed this part

Did*

I think he killed his father because he was an asshole in the first place, I think he killed his mother because she was somehow weak or something like that..he’s a psycho so we can’t tell exactly what he thinks..(*´-`)

It still hasn't been fully explained

I think we will later know why he killed his mother, I think this bitch is actually very important for the story.

I think it too but in the last chapter Sangwoo called Bum “dramatic “ like his mother and in his flashback she seems a weak and passive woman so Im 60% sure about that.

I think that he most likely killed his mom because she was going to call the police on him or possible pushed him away because he did kill his dad to help his mom and he couldnt stand the rejection and snapped