Najibullah Zazi in Aurora, Colo.

Bomb Lab?
The same day he shopped at the Beauty Supply Warehouse, Zazi checked into a room with a kitchenette at the Homestead Studio Suites a few miles away. When investigators searched the room, they found traces of acetone in the vent over the stove — an indication, they say, that someone had been cooking a bomb.

• An Enemy Within: The Making of Najibullah Zazi