Oh no, I'm so sorry to hear this.
Losing them so suddenly really takes a toll. I know that my Dovey will be there for Sheldon, waiting and happy to give him a warm little poof of feathers to curl up next to. After all your kinds words when Dovey passed, I only wish I had words to console you now.
Sometimes nature is cruel and surprising. But Sheldon isn't in pain now and he didn't suffer. He lived a good life with you, the best a bird could ask for.