if you want to create your own map for this then you gotta add the following:
3 to 15 pinkys
an arch vile in the area with the most chewy folks
VALUES HERE
Categorys: Humans + Resistance. Combine.
Weapons: { "weapon_ar2", "weapon_pistol", "weapon_smg", "weapon_shotgun" },
models: models/Police.mdl. models/kleiner.mdl. models/Police.mdl. models/Zombies/Classic.mdl.
CHANGING NPC CATEGORY THING WONT CHANGE FACTIONS. IT ONLY CHANGES WHERE TO FIND IT