When Louis get his pills - help me please!

So I want to make my own shot at one of those “what happens when x gets his x”, but I cant seem to find the background song used in anyone of them?

this background song. What is it called? Only thing I know is that it is from l4d.
Thanks

The map is always or mostly cs_assault, but the music is “The Monsters Without” from Left 4 Dead 1.