. >> that was united flight 175, as gordon haberman joined his wife. >> i threw a cup against the wall didn't know what tower she was in. we didn't know where she was. >> the search for andrea haberman, john niven, and nearly 3,000 others would become the passion of dr. charles hirsch, the city's chief medical examiner. he raced to the base of the burning towers with a team that included a young scientist named mark desire. >> both towers were standing. they were on fire. we parked our truck. we set up a temporary morgue and began to preserve the evidence. wasn't long, i received my orders. i picked up the gear box and the south tower crashed. the plume. you could see the steel and fire coming down. i thought this is it, this is how i die. >> the south tower, with john niven inside, foundered after 56 minutes. >> as you're running away from the collapsing south tower, you were heading for a door in an adjacent building and then you got blasted off your feet. >> yeah, just knocked me right out of my shoes. never made it to the door, but it was enough to get me through the -- partially t