It's circumstantial. In your situation, I might have stopped, because I have more medical knowledge and equipment than most who aren't medical professionals. But if a crowd has collected and professional responders are close, there's nothing wrong with driving on.

Years ago in a very bad neighborhood I saw something similar -- the man looked like he was dead. My response was to call the police without stopping.

In my opinion, there are circumstances where I will always act if I can. If nobody else is around besides myself, I will act. If nobody else is willing to act, I will -- and I've seen this almost every time I've witnessed someone getting hurt. And of course, if it's my friend or family member, I will act.