Confused by the end

When the movie ended, I had no idea about what I had just watched (the final scene, chapter 16 on the DVD). So I watched that scene again.
1. Brummel takes the key to the wardrobe room and goes downstairs to look for evidence. Why does he leave the suspect alone?
2. Gill takes an elevator down and gets there first. He throws a switch which turns the lights (off?), the area glows red (from the exit signs?).
3. Brummel then draws a gun and comes looking for Gill, apparently they are on the stage level now. Again, why did he leave him alone upstairs in the first place?
4. Brummel dodges a couple of falling objects, and fires a gun toward Gill.
5. A counter weight is swung toward Brummel, striking him and knocking him out. Gill stumbles out and we can see he has been shot in the stomach.
6. Gill drags himself over to the unconscious Brummel, takes his gun, struggles to his feet, and begins to replay the characters he used to lure his victims. He fires the gun a few times in the air, and toward the empty auditorium.
7. Gill collapses on the stage and prays.
8. He looks out at the auditorium, and Brummel is standing there watching. How can that be?

What am I missing?