Killzone is a FPS developed by Guerrilla Games (known as Lost Boys before) and released in 2004 for the PlayStation 2. It seems that the project was originally planned to be a Playstation 1 shooter titled “Kin”, but after Sony saw their tech demo in 1999, they asked to Guerrilla to switch it to the new console. Below you can see the original Kin / Killzone pitch video, that Lost Boys created 5 years before the final release. This footage was shown at the GDC Europe in August 2010 during a keynote by Hermen Hulst, Managing Director of Guerilla Games. As you can notice, the game and the characters looked a lot different, but we are not sure if the video was still related to the PSX project or it was already changed into a PS2 title.
Thanks to Unclejun for the video (from the Killzone Collector’s Edition) and to Killzone for the link to the GDC Europe article!