Mico: ZKILLER is an Early Access FPS, Arcade like action game that was originally an FTP mobile game released last May 4, 2018 that was developed by Chainsaw games who recently ported the game to pc on July 25, 2018 for $5. In ZKILLER you fight to survive waves of zombies similar to Killing Floor.
Source: N4G PC ZKILLER Preview A horde of zombies that shouldve stayed mobile | Sirus Gaming