Responses
I agree. In earlier chapters when he takes bum for a hike, he states him & his mother were eating apples as the father laid in the back not eating apples. Right before he leads Bum to where his father was buried. So assuming that the father was already dead in the car and buried him out in the woods or w.e.
"But I haven't killed a man since the death of my dad you see...I guess you are lucky."
-Sangwoo ch.2 page43
Maybe his mother forced him?Or maybe they did this together.