Various lines of evidence (genetics, morphology, etc.) point to the birds as the last living dinosaurs. However, they come from one major group of dinosaurs, not both, so one group of dinosaurs is, indeed, gone.
Work Step by Step
See the book where it moves from reptiles to birds and the evidence there about birds being descended from dinosaurs. In a monophyletic analysis, they would fit within the dinosaurs, and those together within the reptiles.