Tripwire Interactive's recent co-op themed zombie shooter Killing Floor has become a big download sales hit on Steam, showing up in the service's top 10 for the first several weeks of its release.Today the company announced that they will release both free and paid DLC content for Killing Floor, starting with a free map and two new weapons in what's being called the "Heavy Metal" pack.

The map itself is called Foundry and as one might expect it takes place in an old iron works factory. The two new weapons are an AK-47 machine gun and (as shown above) a Japanese Katana sword. Tripwire also announced plans for a paid DLC download for the game that will add four new playable characters. So far there's no word on when either downloads will be released nor what the price will be for the paid DLC expansion.