OP, good job for having the heart to take a look at the situation. Too many people would not involve themselves and though many people would say to not get involved, your moral compass tells you to aid those in trouble.
Anyway, self-diagnose just a little... weak legs from a sudden adrenaline dump? I have seen it with traffic accident victims who virtually collapse after the the situation starts settling down. This was a high-stress situation and your reaction doesn't seem out of the ordinary.