Thursday will see the arrival of a hefty update for co-op survival shooter Killing Floor as well as a long weekend of free play, developer Tripwire Interactive has announced.

The "Level Up" content pack will bring three new maps, one monster and seven weapons, which IGN preview reveals to be an automatic shotgun, a healing gun, two rifles, plus grenade launchers and proximity mines for the brand new 'Demolition' class.

Those eager to start the monster-slaying survival fun can already pre-load Killing Floor on Steam for when the long weekend of free play kicks off on Thursday.

Developer Tripwire has announced a free new pack of downloadable content for its co-op zombie shooter Killing Floor.

The pack will include one level, titled "Foundry," along with two new weapons: the AK-47 and katana (pictured below, left).

Tripwire is also planning to release a paid DLC pack soon, which will include "four new playable characters including a Horzine foundry worker and a soldier in prototype Horzine body armor."

Killing Floor--an enhanced standalone PC release of Shatterline's Unreal Tournament 2004 PC mod handled by Red Orchestra: Ostfront 41-45 developer Tripwire Interactive--will hit Steam on May 14, store operator Valve revealed today.

Those that pre-order the six-player cooperative zombie shooter will receive 25% off the full asking price, making it $14.99 for those in the US. A scream-filled trailer was also released, examining the various monsters, weapons, and features of the game.

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Red Orchestra developer Tripwire Interactive is creating another full retail game based on an Unreal Tournament 2004 mod, this time the co-op survival horror Killing Floor.

Perpetuating video games' colourful image of London, up to six players are trapped in the hellish city after a mad scientist's twisted experiments escape and wreak havoc.

To fend off the relentless waves of nasties, players have a sizeable arsenal--with flamethrower--and can weld doors shut to delay the fiends. Throw in an SDK, persistent character perks and Steamworks integration, and your monster mash is complete.

Killing Floor is to be released on PC for download through Steam "in the near future." If you want to check out its source material, the original mod is available on FileShack.