I've never been in the situation where I've had to help someone at my own risk. But I do recall when I was a meeting planner, we were in a convention hotel in the convention area, and I was behind the registration desk. Just as 1500 people let out from the break-out sessions, a man had a grand mal seizure in front of me - and his forehead was the first thing to hit the carpet - the carpet that was like 1/8" thick with solid concrete beneath it. Needless to say, headwounds bleed, he was still seizing and everyone just went still with shock.
I have no idea what came over me, but I jumped on the hotel phone, had them call an ambulance, then jumped over the registration desk, pushed people back, yelling if anyone was a doctor or EMT. Luckily, one of the attendees was an EMT (this was a real estate conference) and she rushed to his side. I, meanwhile, went into 'fence' mode - pushing back the curious, pulling people I knew into a ring around the guy.
Then my boss showed up. My boss who couldn't stand the sight of blood. Luckily her husband was standing right next to her to catch her when she fainted.
The ambulance arrived quickly, cleared out the area and I went behind the registration desk, adrenaline running high, ready to help revive my boss then decompress. BUT then the temporary worker who was working with us said, "I don't feel very good." Here, the girl was a diabetic and she was going into shock - totally unrelated to the seizure incident, but she was young and obviously not caring for herself properly. So, there I went, back on the hotel phone and looking for orange juice.
Once that was taken care of and the break-out sessions re-started, I found a nice corner to crawl into and have a good cry. It seems, instinctively, I'm a good person to have around for an emergency (and since having children, this theory has-unfortunately-had cause to be proven true), but I absolutely fall apart afterwards.
God willing, I'll never have a reason to see what my reactions would be if my life were at risk. Your perceptions change when you've got kids. I'd lay my life on the line for them, but for a stranger? I'd like to think yes, but I rather think I wouldn't because I wouldn't want to leave my kids without their mom. But, like I said, God willing I'll never have to find out. Hats off to the subway rescuer! He's a hero.