Final answer:
If you witness an event and are alone, leave the child to activate the emergency response system and get the AED.
Step-by-step explanation:
If you witness an event where a child needs help and you are alone, the first step is to leave the child and activate the emergency response system. This can be done by dialing emergency services on your phone or finding the nearest emergency call button. Once you have done that, you should locate and retrieve an automated external defibrillator (AED). AEDs are portable electronic devices that can deliver a shock to someone's heart in the event of cardiac arrest. They are typically found in public places and are designed to be used by laypersons