A 32-year-old man is brought to the emergency department with a gunshot wound to the left anterior chest at the 4th intercostal space. On examination, he is conscious, blood pressure 95/60 mmHg, heart rate 118/min, respiratory rate 28/min. There is a small entry wound with a surrounding zone of abrasion and soot deposition. Chest X-ray shows a pneumothorax and mediastinal widening. What is the most likely distance from which the firearm was discharged?