Yeah, I found an M4 and 4 mags in Berezino and figured i'd get out of town so I wouldn't have to use them all immediately. And then I was attacked by 115 zambies. They respawn faster than you can kill them.
The zombies are in the game as "animal" assets and not actual humans. This allows them to ignore AI scripting and shit. Or something. Either way the ARMA engine is not cut out for aggressive animals so it handles them terribly. Wave of the future.
Oh man. ARMA's AI is made for realistic combat. Adding NPC factions would be hilarious, if they were hostile to you. You would be killed from kilometers away, routinely.