Responses
I think if it was Bum, he'd still be defending Oh since he's keeping him from killing an LEO. If Oh kills Sung, then people will get very suspicious, and at some point they'd go to Oh and find the body, or at least evidence of his other murders.
Please don't let it be bum's blood , well you know those drama where out of nowhere they appear to defend that person and got stabbed like srsly i will flip all of the tables in this house