Not really a song.
The non band songs present in the movie were scored by Don Davis.
That particular music in the movie was titled "lobby shooting spree" it's on the 2nd disc for The Matrix: Original Motion Picture Score. -
http://en.wikipedia.org/wiki/The_Matrix:_Original_Motion_Picture_ScoreThis post was edited by Arsenic_Touch on Jun 2 2014 12:39am