Back ground:
In the new patch there is an algorythm that spawns new zombies if you fire off your gun. These zombies seem to spawn anywhere within 100 metres. There seems to be a 10 second cool down for this. For example there does not seem to be a difference in how many zombies spawn if you fire one shot or a burst. However there seems to be only a 10 second cool down because if you fire, have a zombie spawn, and kill it 10 seconds after the first shot, another will spawn.

Bugs:
#1 Zombies will spawn right beside you sometimes. My friend and I were in a field just outside of Zelenogorsk and sniped a zombie at long range. Since we were in a field we could see the zombies spawn from the gun shots and some of them spawned a few feet from us or right beside us attacking. This mechanics is ok inside a city, but its not like zombies could sneak up on you when you are in an open field.

#2 This new algorythm is designed to make the number of zombies more realistic, however having them spawn in random locations (i.e. teliport in ) in not realistic. Zombies should already be spawned in a city. Say 100 zombies for a big city like Zelenogorsk, and as you come up to the city you could see them all (which would look awesome).
Also there does not seem to be an end to how many zombies will come from gun shots in a certain area. If you shoot a zombie, and another one spawns in the distance and it takes time for it to run to you, shooting that one will spawn more zombies since it seems that there is a timer and it resets.