27-year-old John Tierney was still a probie in the FDNY, having graduated the academy only in July. That morning he had just finished his shift when the call came in. He was told he didn’t need to respond, but he insisted, riding on the lap of another firefighter for the short ride to the WTC because there was no other space on the truck. For the past 18 months, he’d been learning to play the guitar, practicing until he had blisters. He especially favored Dylan and the Beatles.