If a medical emergency victim is not breathing, such as after a heart attack, call 911 and administer CPR. The American Red Cross3 suggests 7 CPR steps:
Check the scene and the person
Call 911
Open the airway
Check for breathing
Administer chest compressions
Deliver rescue breaths
Continue CPR steps until help arrives
Once a first responder arrives, it's essential to write down everything you remember, including an explanation of what occurred, witness testimonies with contact information, and resulting damages. Photos of the situation may also be helpful.