Padilla and an accomplice approached Zubeida with a new idea -- to go to the U.S. "to detonate a nuclear bomb they learned to make on the Internet." Zubeida did not think the concept was "feasible," and pushed the idea of dirty bombs.
With a letter of introduction from Zubeida, Padilla met Mohammed, considered the mastermind of the Sept. 11 attacks, in March 2002. Mohammed was "very skeptical" of the dirty bomb concept, the intelligence said, and suggested instead that Padilla and his accomplice undertake the apartment building operation.
The plans called for Padilla and his accomplice to locate up to three U.S. high-rise apartment buildings with natural gas supplies. "They would rent two apartments in each building, seal all the openings, turn on the gas, and set timers to detonate the buildings simultaneously at a later time," the report said.
Selection of the target city was left to Padilla. He told investigators that Mohammed preferred to hit targets in New York, although other options were discussed. The report said that according to other sources, Padilla was instructed to conduct the operation in the central U.S., along the U.S.-Mexican border, perhaps in Texas or California.