Over the course of several months , the FBI listened to Zazi 's phone conversations . In August 2009 , the FBI overheard him speaking about mixing chemical substances . It learned that in July and August 2009 he and his three associates were buying large quantities of hydrogen peroxide and acetone products from beauty supply stores around Denver , Colorado . Workers at the Beauty Supply Warehouse in Aurora , Colorado would later tell CNN that Zazi was " a regular " at the store and had made several recent purchases shortly before his arrest , telling them that he had " a lot of girlfriends . " Hydrogen peroxide and acetone are components of triacetone triperoxide ( TATP ; also known as acetone peroxide ) - based bombs . TATP was also used in the 2005 London subway bombings , and by Richard Reid , the " shoe bomber " . According to the United States Department of Justice , jpeg images of nine pages of handwritten formulations and instructions for making and handling TATP and other explosives were found in one of Zazi 's email accounts ; they mention that acetone is found in nail polish remover , and that hydrogen peroxide can be found in " Hair Salon - 20-30 % . " Zazi checked into an Aurora motel suite on August 28 and on September 6 and 7 , and used the room 's kitchenette to create chemicals for use in bombs . Authorities examined the kitchenette , and found traces of chemicals in the vent
2005 London subway bombings
7 July 2005 London bombings
Najibullah Zazi