Final answer:
When arriving at the scene of an unresponsive and pulseless patient, it is important to initiate CPR, apply the AED, and deliver a shock if needed.
Step-by-step explanation:
In this scenario, as the first responders to an unresponsive and pulseless 70-year-old man, you should begin CPR, apply the AED, and deliver a shock if it is indicated. The paramedic unit is en route to the scene but will arrive in approximately 5 minutes. It is crucial to start CPR immediately to maintain blood circulation and provide oxygen to the vital organs. Applying the AED can help assess the patient's heart rhythm and deliver a shock if necessary to restore a normal heartbeat.