They could be elsewhere in the room… but the pictures do kinda look like somebody with a bucket of brass tossed a few handfuls around the scene for flavor/staging effects. Certainly the shot-up door with the gun caught perfectly framed in the doorway looks somewhat staged. 
“Certainly the shot-up door with the gun caught perfectly framed in the doorway looks somewhat staged.”
That rifle on the floor had probably not been fired. No magazine in it (it is above on the counter). Gun is positioned perfectly parallel to the wall - shooter had OCD tendencies I think - see the perfectly stacked magazines in other photos.
Shooter’s body was found off to the left of that door - he was found where he would have been able to cover the main door (shot up one) and the inner door to the adjoining room.