It's strange the things impulse leads us to do. On that day, would any of us have thought to have stopped and picked something up off the ground? I don't think I would have.
This link to a tweet is about a letter in a red envelope that a British businessman, who was one of those fleeing the destruction in Manhattan on 9/11, saw on the ground and scooped up impusively.
He then forwarded it from London to its destination in LA. In a short video (~3.5 minutes) the recipients talk about how they felt.