I’ve never been at a horse event with a fatality. The one thing I do know for all accidents and other medical events: For heaven’s sake have a radio channel dedicated to medical incidents, and if something major happens get the EMT and helper traffic over to that channel.
The entire volunteer group with radios, as well as anyone that can hear them, does not need to be listening in on the many radio messages and details about the patient. Not only can it be upsetting to people listening who aren’t involved, but it’s sharing private info about the patient that the patient might not welcome.