It’s a dicey issue most people aren’t aware of. It varies from jurisdiction to jurisdiction. Some places only an MD can pronounce death. The implications that unfold from that policy are profound but most people can’t anticipate them.
"....“No adult non-traumatic or blunt traumatic cardiac arrest is to be transported to a hospital with manual or mechanical compression in progress without either return of spontaneous circulation (ROSC) or a direct order from a medical control physician unless there is imminent physical danger to the EMS provider on the scene,” the directive said."
Locally, faced with dire cardiac events EMTs are in radio contact with nearest hospital's ER "medical control officers" presenting symptoms, vitals, and initial treatment. The remote ER physician makes the decisions.
Unattended deaths present potential legal problems as to cause...potential homicide needs to be ruled out, so transport is to hospital or medical examiners, IIRC...current events have added the pandemic problem...not just hospital overflow, but ME and morgue overflow. As you've pointed out on other threads once that critical number is reached battlefield triage rules must be applied. The toll on civilian first responders and medical personnel becomes enormously heavier.