Final answer:
The priority upon arriving at the scene should be to quickly gain access to the patient.
Step-by-step explanation:
The priority upon arriving at the scene of a young male with abdominal pain in an apartment complex should be to quickly gain access to the patient. This means assessing the situation and finding the most efficient way to reach the patient and provide medical assistance. While notifying the dispatcher, assessing the scene for potential hazards, and placing a paramedic ambulance on standby are important steps, gaining access to the patient is the priority in order to start assessing and treating the abdominal pain.