The very first thoughts going through your mind should be, "is the scene safe to enter?", and "do I have my body substance isolation?" (BSI). Make sure you're safe first, because you won't be any good to the patient/victim if you get yourself hurt. Following that is your initial assessment followed by ABC's (airway, breathing, circulation). After that comes whatever treatment is necessary for the specific injury or illness.
The very first thing you do is look for hazards to your safety. Then get someone else to call 911 and have them guide the response personnel to your location.
Then you need to identify your self to the casualty, tell them you know first aid and offer assistance. If they are unconscious then consent is automatically implied. If they are dazed and confused try to get them to acknowledge you, again state that you have first aid and can assist them, if the nod that they understand then help.
If they refuse aid then observe them till the paramedics arrive. If they pass out then you can assist. It's a stupid law and it only applies in some places, but it's a law none the less. If they grant consent then you carry on with your ABC's and full assessment, carry on as per your training.
When carrying out emergency first aid whose safety is your first priority
me
first aid is very important. It can save your life.
Further injuries or paralysis...
Inject for 10 seconds.
Call 911 first! Then the rest is based on the situation and your knowledge with administering first aid. Above all if you don't know what to do, keep body warm to keep from going into shock. Rephrase your question as to what first aid situation you are referring to.
10 seconds
the arm is broken
3-5 seconds
Atropine is noramlly administered via an auto injector to combat the bradycardia and dissarythmias
10 Seconds
10 seconds
10 seconds
Airway