@Daisee LT Kangs brother went missing and the retired officer Kim, who just shot himself, was asked to keep an eye on LT. Kangs brother by the corrupted cop Ahn Jae oh (the senator now who got strangled by the bag by Rok in before chapters who was going to marry that woman who started it all) but they went over a mountain cliff on accident and LT Kangs bro hit his head and died and he covered it up and buried him underneath that tree instead of reporting it. The record tape had all the plotting of killing the major players in the red light district by senator Ahn and madame Jeon that Kangs brother had and thats why officer Kim went after him, he helt guilty for all his sins so Kim exposed everything and told Kang where his bros body was and then shot himself, he basically just gave Kang the evidence he needed to take down that bi*** Jeon