Complete the BRIDGE level without a kill. [Bronze / 30G]

Location: Bridge
During the entire chapter "Bridge" you may not kill any enemies. This chapter is pretty much at the end of the game. You can basically do two things: sneak around enemies quietly or run through the level as fast as possible. Running is easier and you won't run out of air (your gas mask consumes air over time and you will die if it's empty). Just don't attack any of the enemies at all and try not to get hit. Make use of your med packs if needed.