Wow, I love the way you play with different meanings of the same word and move from one to the next in a series of poetic connections. It's very powerful.
I think you particularly get into your stride with this later in the piece and I think you could afford to lose a few sentences earlier on which would, in my view, make it even more striking.
I would start by losing the very first sentence because it's a bit clichéd and doesn't really need saying. You could instead start with 'My brother's body was found washed up...'
I would also cut the start of the second paragraph because the simile of hunter and prey doesn't fit with the rest of the passage. I'd start this paragraph with 'The thought of him struggling...'
I would possibly do something about the bit where you talk about 'deciding' who reads the note as I think this breaks the flow a bit. It depends how important it is to get across that the mother can't bring herself to read it. I think it would read fine if you slipped straight from '...note in his bedroom.' to 'He spoke of his dreams...', unless the bits in between are important to you.
Finally, I think you could end the scene on 'But his death had power over us.'
You have a beautifully moving and powerful scene here with what I think people would say was a very distinctive voice. Do ignore all my cuts if you want to. I am a very inexperienced writer myself and would be incredibly proud of I'd written something like this.
Thank you for sharing. I'd love to read more.