Sultan knows

After RK's drunken rambling Sultan pretty much knows Rishbala's whole love story better then RK and Madhubala themselves. He knows that RK tried to ruin MB's life and she, without even trying actually made his life miserable instead. And he also knows the one thing that no one, including RK himself, hasn't realized yet: that RK is in complete turmoil and angst over Madhubala forgetting him and moving on. On another note i thought Sultan overlooked RK's phone call with Aryan, so why the gun at the end? Or is he doing it because RK confessed that he ruined MB's life? :S