Literally all professional literature on the subject suggests the following:
Remain calm, be aware of your surroundings, and closely evaluate the scene to protect yourself and others from further injury.
Do not move a critically injured person unless instructed by emergency medical professionals.
Do not try to drive someone who is critically ill or injured to a hospital unless there is no way to summon emergency help.
Call 911 or ask someone else to call: - If you think there is a medical emergency, - If the crisis could get worse left untreated or not treated properly.
Listen carefully to the 911 dispatcher's questions. Answer them calmly and quickly.
Remain on the line until the dispatcher tells you it's okay to hang up.
Ask someone to wait outside to meet emergency personnel if it is safe to do so.
Paramedics may want to know a brief summary of the circumstances that caused the emergency. Remain calm and cooperative as they gather information.