Ahhh I just don't understand mangas/manhwas sometimes... How did he get caught? I mean was there like a camera or....? UGH LOL I HATE MYSELF RN I CANT UNDERSTAND
As the boss mentioned when handing over the file, the mafia could possibly already know at tht point that Mr Spy was in fact from the army (the boss mentioned that the mafia had good informants). Other than that, I'm suspecting that Mr Mafia-Boss somehow knew his old friend was lying (maybe because he remembers a certain behavior of his friend when he's lying or he can just tell by some other reason).
The mafia could also have spies in the military. It's russia after all. :v
Didn't the boss said that he knew something isn't right about the officer when they met at the theater? Because the officer never went to a theater since the last time he went together with the boss to met his mother.
That's why he knew the officier lied and maybe immediately told his subordinate to check the officer's background
MAMA DON'T PLAY THAT GAME SHE ABOUT TO ATTACK SOMEONE LIKE A GORILLA.