You just don't understand how this video could be real. How could your brother have come out into the forest to start changing into an animal for real? You feel happy for him if his fate is truly what you see here. You were worried that he'd been kidnapped or murdered or something--he was always very trusting and vulnerable as a child and largely remind that way after you both grew up. He always used to play at being an animal when you were kids, and when he was a teenager he got really into forest animals and especially beavers. He would have wildlife posters all over his side of the room and liked to build piles of sticks to sit in during camping trips as his little "beaver dam." On the night when you came out to him as gay in your shared bedroom, he admitted to you that he thought he had been born in the wrong body and would have lived his whole life wild in the woods if he could.
Now here was a video recording of your brother showing off his clawed paws with long teeth starting to jut down from his upper lip. His feet became webbed, and his whole body started to shrink. He spoke his message while he was still able:
"I found a magical amulet at a garage sale two or three years ago, which will turn people into an animal for as long as they want. I finally built up the courage to leave my human life behind me once and for all. I couldn't let anyone know because they wouldn't believe me, and it would only make them more upset when it was time to leave them. But wanted you to know the whole truth because you were the only one I ever told about what I really was deep down inside."
He was about half the size of his adult self now, and his body hair had lengthened and thickened. A skinny tail was dangling between his legs and a long whiskers were starting to sprout from his cheeks.
"If you're interested in the amulet," he continues, "I'm going it under the maple tree with a purple X painted on it. I'll turn back into a human after this video so I can send you this, I just wanted to show you my transformation so you'd believe me. After I'm done with my final task, I'll turn back into a beaver for good. Remember, I love you! Wish me luck in the wild!"
All his hair was unmistakably long bray fur at this point. His tail had darkened and widened and he was slapping it up and down like a paddle. He was even smaller now and looked about as small as he was going to get. He waddled out of the frame, and in another few seconds, the video was over.