We exited the doors on the west end of the solarium onto the outdoor harbor plaza, where we could see small yachts and recreational sailboats bobbing in the World Financial Center marina. We turned back toward the solarium mall, behind which the World Trade Center towers were clearly in view -- we weren't more than 500 yards from them. A large crowd was beginning to form. Very little of what I saw made sense. There was a hole in Tower 1, but we were looking at it from an oblique angle, and from our perspective, it looked insignificant. The building's immensity dwarfed the gaping hole, and I misjudged how deep a wound it had sustained. But clouds of thick black smoke were pouring from it, and from a second, smaller hole that faced us. There was one more thing I remember distinctly: Pieces of paper filled the air, as if a parade had been scheduled on Broadway just a few blocks away and the parade-goers had been confused about where to drop all the confetti. It looked far too much like a celebration for me to grasp what was happening. Everyone around me was talking on a cell phone, learning from loved ones about the various explanations that were being offered on television and radio broadcasts. The most talked about explanation was that a general aviation plane had mistakenly flown off course, or that its pilot had suffered a heart attack. I was discussing the possibilities with Ron, who knew a good bit about construction and buildings because his family was involved in general contracting. "Could a Cessna do that?" I asked him. "No f**king way," he said. "Then it must be a bomb?" I asked. That was not an unlikely possibility. I had been trading in NYMEX's previous home at Four World Trade Center on Feb. 26, 1993, when a truck bomb exploded in the parking garage below Tower 1, shaking the trading floor. On that day, I had managed to leave the floor, walk through smoke-engulfed hallways in the mall leading to the subway lines and catch a number 1 subway train back home to the Upper West Side before the Metropolitan Transit Authority recognized the problem and shut down the subway lines.