Maybe there is a low-level natural gas leak. The company doesn't care, because it's not like they get money for that gas or anything, so they wouldn't miss it. And maybe the gas makes everybody addled. I know, natural gas mostly knocks you out and then you die in the explosion, but we are speculating here, so maybe this is a special type of natural gas that doesn't have the smelly additives, and just makes you loopy.
So, Adam breathes this stuff every day (well, ok, he doesn't actually go to school anymore, and probably isn't walking around town where the gas leak is, but maybe they hooked up some lines from the gas leak to his house). He goes nuts. So do all the teachers and students at the elementary school.
Well, we know the cops are affected, because they are touching dead and injured bodies, and we know that cops using their full faculties never will be seen touching bodies that need medical help, or escorting them out of a building or anything like that.... 
And this could explain the EMS folks being told to "stand down", like they were sleeping on the job.
It could certainly explain Crazy Gene -- he's just addled by the leaking natural gas:
Except how do you explain Gene performing this satanic ritual, attempting to re-animate various animals he had previously turned into stuffed dolls?: I mean, that's not the act of a guy who has a natural gas high. Not that there is any acts known to be committed by people stoned on natural gas, given that you can't actually get stoned on natural gas.