I have another theory, which I'll call the "
Schrodinger's Cat" theory.
Gnegg is sitting in his chair, pondering his elaborate suicide. He then goes to his time machine, and sends himself an hour into the past, where he sees himself--Gnegg1--sitting in the chair. Gnegg2 aims his gun, and fires at his past self.
The gun fires, the bullet flies, but vanishes an instant before it would have struck Gnegg1. Instead, Gnegg2 is struck in the chest by an invisible bullet. He dies, collapses to the floor, and his body and gun both vanish. At this point, Gnegg has locked himself into an infinite loop (at least, from his point of view). Gnegg1 never sees Gnegg2 fire at him, and does not percieve any of this, except perhaps as the idea entering his mind.
This theory is based on the idea that any event which has already occurred from a future viewpoint must be allowed to occur in the present viewpoint, because it already happened, and that timeline has already been established. (the parallel universes/timelines idea frees us from such restrictions, but that's another theory). When Gnegg2 fires at Gnegg1, he does, in fact, kill "himself", but Gnegg1 must still be allowed to do this an hour later, because Gnegg2 has already established the timeline. Therefore, Gnegg2 fires, but the effect of his actions are delayed until Gnegg1 completes the actions he's been locked into. Of course, by then, he has become Gnegg2! So Gnegg2 fires at Gnegg1, but kills himself.
From an outside perspective, let's say his neighbor hears the gunshot. He goes over to Gnegg's place, and finds Gnegg sitting in his chair, dead, with a bullet wound to the chest. Why is he in the chair, and not on the floor? Because that's where he was shot. When Gnegg1 is shot, he becomes Schrodinger's Cat; both alive and dead. While he is in fact killed in the chair, he is also temporarily alive--a quantum duplicate created for the sole purpose of completing the timeline. Once all actions are accounted for, continuity is restored, and the duplicate ceases to exist.