Firefighters, police, EMT's, soldiers showed up, first by the score, then by the dozen, finally by the hundreds. Each hero committing their own separate acts of courage great and small.
Those who witnessed it live or on TV will never forget that day. It's one of those events of such magnitude you remember where you were, who you were with, and what you were doing at the time. Some memories fade over time, this is one we should hope won't, lest we forget what it is we never want to go through again.