He may have had the World Trade Center in mind all along, but he seems to have chosen it firmly as a target only after arriving in New York. He decided that he should construct his bomb so that its force would wreck the central beam of one of the center’s 110-story twin towers. Yousef hoped that as the first tower fell it would topple the second building. He calculated this would cause about 250,000 deaths, which he believed was roughly the number of casualties caused by America’s atomic bombings of Hiroshima and Nagasaki during World War II.
