An unresponsive 21-year-old male was shot in the left upper abdominal quadrant. His skin is pale and diaphoretic. You auscultate clear lung sounds, and his neck veins are flat. His vital signs are P 116, R 20, BP 100/72, and SpO2 is 92. What is the most likely cause of his hypotension?
1) Hypovolemia
2) Cardiac tamponade
3) Tension pneumothorax
4) Distributive shock