Ordinary people don't know that there are many types of heart disease. Traffic police only know that many heart disease patients carry nitroglycerin tablets, assuming all heart disease patients should be taking nitroglycerin.
How could the young man possibly have a myocardial infarction? The symptoms don't match that condition; it doesn't seem like a vascular issue, but more likely something to do with the valves or other parts within the heart. Without diagnostic equipment and clear understanding of the condition, doctors dare not administer medication recklessly, especially when the blood pressure and heart rate aren't critically low. One wrong injection could kill rather than save the patient.
Patients with such heart conditions need to be monitored even when given injections, and right now, that's simply not possible. The best course of action would be to quickly get him to a hospital for treatment, which might require emergency surgery.