Don't jaywalk, people.
I would definitely have stopped and called the police. I might have even gone to check on him and reassure him that help was on the way. But, there's only so much one can do who is not trained to handle medical emergencies. If you touch him and hurt him more, you can be sued (good samaritan laws be damned). If you're in the middle of the street, you could get hit yourself.
But, I could have sworn that one of the people who ran into the road put a phone to his/her ear. Maybe I was just seeing things.