How does Gene feel immediately after Finny's fall?

Immediately after Finny's fall, Gene, unshaken, jumps into the river, seemingly without remorse or concern for his friend. It almost seems as if he sees himself as victorious.

Holding firmly to the trunk, I took a step toward him, and then my knees bent and I jounced the limb. Finny, his balance gone, swung his head around to look at me for an instant with extreme interest, and then he tumbled sideways, broke through the little branches below and hit the bank with a sickening, unnatural thud. It was the first clumsy physical action I had ever seen him make. With unthinking sureness I moved out on the limb and jumped into the river, every trace of my fear of this forgotten.