A 35-year-old male is undergoing elective abdominal surgery under general anesthesia with sevoflurane and succinylcholine. Fifteen minutes into the procedure, the anesthesiologist notices rapid rise in end-tidal CO₂, muscle rigidity, and core temperature climbing to 39.2°C. The structure marked **B** in the diagram (sarcoplasmic reticulum with RyR1) is suspected to be dysfunctional. Which of the following best explains the pathophysiology and immediate management in this patient?