Ending 1
If you don't get shotgun, or get it and don't load it:
The bad guy at the end pulls out a taser, and you will do nothing, except, presumably die.
Ending 2
If you get the shotgun and load the red shell
Or
If you get the shotgun and load the red shell in the left chamber and the green shell in the right chamber:
The bad guy at the end pulls out a taser, and you will shoot him in the leg, a truck driver will see you walking out of the woods afterwards
Ending 3
If you get the shotgun and load the green shell in the left chamber and the red shell in the right chamber:
The bad guy at the end pulls out a taser, and you will shoot at him and miss (miss might be the wrong word, I think the green shell is a blank), then shoot him in the leg, a trucker will see you walking out of the woods afterwards
Ending 4
If you get the shotgun and load the green shell in either chamber without the red shell being loaded:
The bad guy at the end pulls out a taser, you will shoot at him and miss/shoot a blank at him, then you will presumably die.
Secret/Bonus Ending:
Get the cell phone, put the battery in it, and call jesus (53787). The room with the computer has a secret compartment in the wall, take the camera in the wall and take a picture of a room (I only tried two rooms, but I think any will work). The cell phone is next to the couch on the top floor, and the battery is in the left mannequin’s left hand. You will get a secret cut scene after the credits if you completed either ending in which you actually escape.
These are all I had the patience to find, (after the second time through I just right clicked and hit play a bunch of times.)