During my first playtrough of this map, i gathered 3 other friends to come with. The four of us had a blast exploring the map, but about a few minutes in we started to notice some zombies spawning. At first we thought that one of us were spawning them in to scare each other. But we soon found out that none of us were spawning them in. The placement of these zombies were too good and subtle to be player placed. There would be scattered zombies in the buildings we explored, some in near the campsites we discovered (the ones with burning barrels), headcrabs spawning in the back of trucks and ambulances, fast zombies popping out of alleys to ambush us on the street, small groups of combine soldiers started appearing as well, and barnacles spawned on the smaller metal bridge (not the main bridge). It really added to the atmosphere of the map, i loved it. Sadly i do not know how to re-create the NPC spawns. Walking around the town for hours in singleplayer did nothing, and so did playing with a 2nd person in multiplayer.

If anyone else has experienced zombies spawning, please let me know what triggers them. If you don't know what triggers them, at least tell me if you've encountered them so i know that i am not going crazy. Thank you