Steven Rosenbaum knew his day was changing as soon as he saw United Airlines Flight 175 hit the south tower of the World Trade Center. He already had several documentary crews with him in his office on Fifth Avenue. Rosenbaum and his wife had co-founded the media company Broadcast News Network. They were preparing to start recording a series for Animal Planet. “We were in the room, in the conference room, watching a large TV when the second plane hit,” he said. “And from that second, everything changed.”