>> reporter: it was fleeting, though. >> it was fleeting, again. our task as human beings is to ask ourselves what is it that gets us to be what we have the capability of being, good human beings? >> reporter: the lessons of 9/11 are also being passed from parents to their children. as brian maguire told us, his teenage son is preparing to become a firefighter just like his dad. >> my son is 18 years old. wasn't born. but seeing what i'm going through, i think he understands how it's still affecting people today. and i'm glad he's taking my footsteps to be a fireman. he just graduated the fire academy. he's going to be a firefighter. i'm proud to see he's going to carry the firefighting tradition on in our family. >> reporter: maguire also remembers the sense of unity and patriotism that rose from the ashes in the days following 9/11. >> hundreds of people. hundreds of people were waving american flags. >> reporter: 20 years later, the survivors of 9/11 are fighting to keep that memory alive too.