Shatterline Productions were the original creators of the Killing Floor franchise, with a team of four developers. Alex Quick did the visuals and Mark Welch did the programming, while David Leung Haslan and Dan Nassick (zYnthetic) did the music.

The first iteration of Killing Floor was total conversion mod for Unreal Tournament 2004, and was released in 2005. They then made several updates to the game, bringing it up to version 2.5.

Tripwire Interactive took notice and they worked out a deal which lead to the first retail release of Killing Floor in 2009.