The music playing in the club is The Crystal Method - two tracks from their album "Tweekend." As Justin heads through the crowd to meet the photographer outside, the DJ is playing "Wild, Sweet and Cool." After the meeting, Justin walks back into the club and the music is now the track "Roll It Up." "Wild, Sweet and Cool" is then used again at the end of the murder.
Both actor Matthew Rhys who plays the murderer, and Peter Falk starred together in the BBC 1 TV adaptation of The Lost World in 2001. Released two years prior to this episode. Interesting though is that Peter Falk played a fanatical religious man and potential murderer in that production opposite Rhys' heroic nice guy.