Q. A 32-year-old man is brought to the emergency department 40-minutes after he was involved in a motor vehicle collision. He lost a massive amount of blood. His BP is 100/60 mmHg, HR is 110/min, RR is 20/min, and his temperature is 37.4 °C. Intravenous fluids and three units of packed RBCs are administered. On examination, pain and temperature sensations are diminished in his lower body below the umbilicus. Vibration and pressure sensations are intact. His muscle strength is 1/5, and his deep tendon reflexes are absent in the lower extremities. What is the most likely cause of this presentation?