When you see a criminally or medically critical situation, such as an extremely intoxicated young person falling down the stairs and becoming unconscious, reach into your pocket, pull out your cell phone, and call 911. Do not wait for someone else to do it.
Related protocol; if someone demands you drink heavily as a condition of membership in their club, it's not a club worth joining.
Honestly, how many dozen people with a cell phone in their pocket refused to make that call? The degree to which people look past situations like this these days is just disheartening.