Do you have to once be a constable to become a detective or SWAT member? What happens if there's a bomb threat at dispatch central, police, fire, ems stations all at once? Would the city go into chaos Why do firetrucks always come with ambulances? Because they're trained in first aid and to assist with manpower. Why do firetrucks come with ambulances when police are already on scene with the ambulance? I don't know, police are trained in first aid and can offer manpower too...