Najibullah Zazi in Aurora, Colo.

The Suspect
On Sept. 19, authorities arrested Najibullah Zazi charging him with conspiracy to employ weapons of mass destruction. Investigators say that during the months he was attempting to realize his plan to build a powerful bomb, he lived in Aurora, Colo., a suburb of Denver. The photo above was taken outside Zazi's apartment on Sept. 16, the day he was first questioned by authorities.

• An Enemy Within: The Making of Najibullah Zazi