Was it really Gene's fault?!?...

I understand that Gene has felt jealousy towards Phineas, but maybe he had decided to seek out his own sense of revenge. After the jouncing of the limb, Gene comments with, "It was the first 'clumsy' physical action I had ever seen 'him' make.(Knowles 60)" He makes the reader confused as to why it should be Phineas' fault for his actions. Maybe Gene believed that Phineas "couldn't ever fall down(symbolically and literally)",but he did which stormed a blast shock into Gene's realization. Yet still, Gene doesn't want to take the blame for Phineas' fall and ends the chapter saying, "With unthinking sureness I moved out on the limb and jumped into the river, every trace of my fear of this forgotten.(Knowles 60)" Why would Gene, after just jouncing his "best friend" off a limb of a tree and hearing that "...unnatural thud.", want to forget every trace of his fear at that just happened?! Is it his guilty conscience or does he really believe it wasn't his fault???