
My instinct tells me that Guwon didn't kill the father. Yes, he's crazy and doesn't understand what's wrong and what's right, but he ain't no lier like he said. Teach on the other hand, has an unreliable memory thing going on and he tried to kill Guwon in his sleep unknowingly. Most likely some trauma that's messing with his memory so with all the things Teach has heard about Guwon and with his memory being messed up, his brain conjured up a fake memory.