What did someone say to you that instantly made you realize their life was in danger?

In the Boston airport awaiting to board when I noticed a older, rotund gent sitting and breathing heavily. I looked closely and noticed he was sweating profusely. I asked him if he had a heart condition or a family history of cardiac disease. He said Yes in-between breaths.

I immediately walked to the gate desk, pushed to the front and very clearly and firmly said there was a medical emergency of a heart attack in progress pointing to the gent.

I returned to the gent, laid him down; opened his shirt, tie, belt, shoes and jacket. By the time I had done this the paramedics were up the jetway, lifted to a gurney and he was gone. Less than 3 minutes from start to in the hands of professionals.

The airline reported later to me that he was resuscitated twice in the ambulance and had survived.