It's tough when a sibling dies, especially in such a shocking way. Please accept my condolences.
My brother died in 2022. He endured about two years of major suffering after a years-long decline. The whole thing was the long term effects of agent orange. I had plenty of time to process it, in fact, when I would visit near the end I could tell he had given up and was praying, "God, would you just get this the fuck over with already?" Yet it still it catches in my throat when I think of him.
Someone once said when a sibling dies they take a piece of you with them. I now know it's true.