This is the third and final version of my mod, and it added: a staircase to the warehouse appeared, while descending the stairs, a bunch of zombies will attack you, and at the end, when you reach the warehouse, one mutant will attack you (though kill him easily). Your main task is to kill all the zombies and burn down the warehouse with the virus. There is one bug when you enter the building zombies (sometimes) just stand to revive them, just shoot. Here is the video: