Brad scrambled back to the edge of the water, but as the newcomer approached, his fear started to fade. There was something interesting about the bear's smell. That realization startled him into taking another look at his own massive, dark-furred body. A bear. He was mostly changed into a bear. A very male bear if his own sensations were to be trusted. The scent of the other bear was bringing on an erection, a hard pink rod sliding out of its furry cocoon like a dog's.
The female snuffled Brad, her need very evident to the former-boy's nose. Curiosity bloomed, and he began to wonder what it would be like to mate with her. If he was still a boy it would be silly, but he was mostly changed into a male suited for the female. He shifted and moved slowly behind her, letting new instincts guide his actions. His almost-human head started to finish changing as he slid over her and prodded. Once. Twice. Then both he and the female bellowed in lust as primal instinct took over. Each thrust seemed to draw more humanity from Brad, his head altering rapidly. He stiffened as his load suddenly shot into the female, the last humanity fading from what was now a grizzly bear.
The bear that had been Brad looked over at the river and saw the curious shape of the boy-becoming-salmon. He remembered what the human had looked like and understood that his friend would join the spawn. That was his friend's life, and the bear would enjoy salmon in the future because salmon always spawned like this. Then the bear that had been Brad snuffled the female, and the two wandered into the forest.
Puck watched the animals leave, tempted briefly to make sure the boy's memory was lost. But no. Better that the bear sometimes think on being a human. Then he flew up to join the others. There would be other foolish mortal boys here to add to the forest's population.