I feel like he was probably aware that the officer would be killed so he protected him?
i feel like this officer will have a really important part ......maybe hell try to kill sangwoo to prove his point i dont know ...this manga is so full of surprises!
.... more likely fear that after the officer was killed, Sangwoo would punish him for the betrayal..... also a little bit of Stockholm Syndrome.
probably all of the theories above are true
i dont know if yoon bum did it for what reason ....if he hadnt hid that officer would be killed for sure!!! yoon bum knows how strong sangwa is ...but why did he hide? stockham syndrome ....