Did anyone else notice that the guy sitting down in the diner breaks the fourth wall for a second? Was there some kind of significance behind this? To me it seemed like the look on the old guys face is saying "Get that camera out of my face. Don't involve me in this."
shareAll the patrons in the cafe break the fourth wall. Most notably, when one of the girls blows her cigarette smoke into the camera.
As to the significance? He talked about being in fear ("angst") quite a bit in his narration. I'm assuming paranoia went along with this, that the killer always felt like everyone was watching him. The breaking of the fourth wall was so that the audience would experience what he felt.