When you get to the part where you activate the panel for the door to open and the horde of zombies come, dont activate yet. Instead, kill all 3 of your partners at that spot. Then wait till they show there yellow lines below you in that room. Wait till all 3 pop-up then let them out. Activate the switcj and survive. Then go up stairs and by the door with booxes will be a assualt rifle and medkit. Repeat this before activateing the horde to get as much as you want of medkits and assualt rifles.