I'm not sure what firefighters do there during an appropriate response, but where I am from they assist paramedics. This can be performing CPR, monitoring and assessing the patient. Packaging and moving the patient. Securing the immediate scene. Dealing with the family present. Gathering vital medical history. Helping paramedics clear the scene.setting up the LZ for a medevac and maintaining the security of that zone... and the list can go on. They generally have plenty to do. If they arent required. They clear the scene fairly quickly.