[PC][2004-2010] Multiplayer Infection Game

This one is a bit of a long shot since I barely remember the game. So basically I watching a buddy place this about 7 years ago. 3D pc game, pretty sure it was first-person. Watched him play an infection game mode, so I dont know if that was the main gamemode. Fairly certain it had zombies, and the game may have had abilities

TLDR: First person 3D multiplayer zombie game with an infection gamemode, possibly had abilities.

Im not expecting anybody to know what the fuck im talking about but Ive been wrong before.