( CNN ) -- A Connecticut store that sold a gun used to kill 26 people last December at Sandy Hook Elementary School no longer can legally sell firearms . Debora Seifert , a spokeswoman for the federal Bureau of Alcohol , Tobacco , Firearms and Explosives , told CNN on Friday the Riverview Gun Sales shop in East Windsor , Connecticut , lost its federal firearms license December 20 -- six days after the massacre about 65 miles southwest in Newtown . That day , after killing his mother in their Newtown home , Adam Lanza drove to the elementary school and shot dead 20 young children and six adults using a semiautomatic Bushmaster .223-caliber model XM15 rifle . The shooter 's mother , Nancy Lanza , bought the Bushmaster firearm two years ago at Riverview Gun Sales , according to Detective Matthew Carl of the East Windsor Police Department . The ATF spokeswoman did not comment on why the store 's license was revoked , including if it had anything to do with the Newtown rampage . But Carl said `` probably the reason the ATF raided the store on December 20 was for poor keeping of the records . '' According to police , on December 15 -- a day after the Sandy Hook shooting -- a man was arrested at Riverview Gun Sales for stealing a .50-caliber firearm . Upon investigation , authorities learned the man allegedly stole a Wyndham firearm from the same shop four days earlier ; in fact , he 'd been arrested in June 2011 for allegedly stealing nine firearms from the store . Newtown shooting details revealed in newly released documents . Afterward , authorities told Riverview Gun Sales ' owner David LaGuercia of the December arrest and checked surveillance images . LaGuercia was not aware multiple thefts had taken place . `` The owner is nonchalant . He is a very non-caring gun owner , very lax in his paperwork , '' said Carl , the East Windsor detective . `` He was eventually closed for hundreds and hundreds of federal and state law violations . '' LaGuercia , the store 's owner , could not be reached for comment on Friday . His store has reopened but no longer sells guns , the detective said , though shoppers can still buy survival equipment and other items there . The ATF conducted more than 11,400 firearms compliance inspections in 2012 . The federal agency sought to revoke licenses in about 100 cases that year , which works out to less than 1 % of all places inspected . According to the ATF website , violations commonly cited in license revocation include `` failure to account for firearms , failure to verify and document purchaser eligibility , failure to maintain records requisite for successful firearms tracing , and failure to report multiple sales of handguns . '' This past week , Connecticut passed what advocacy groups call the strongest gun-control legislation of any state in the country . The law bans the sale or purchase of high-capacity magazines , like the ones used in the Newtown shooting , and requires background checks for all gun purchases .
Adam Lanza 's mother bought a semiautomatic Bushmaster rifle at Riverview Gun Sales . Lanza used that gun to kill 20 children and 6 adults at Sandy Hook Elementary School . The Connecticut gun store lost its license to sell guns six days after that mass shooting . A detective suspects gun sales at the store were stopped due to poor record keeping .