WTF. I am clearly doing something wrong.

I finally managed to get past the four guys at the mall and get to a safe place after killing the first round. I got to a place with cover in the back. I only had one arrow left and killed one more cannibal. But no infected ever came to the mall. Do they not come in Survivor mode? The cannibals opened the door a second time but I only have semiautomatic rounds. No bricks no bottles.