Sandy Hook Elementary School tragedy: Shooter may have tried to purchase gun unsuccessfully

(CNN) -- Investigators believe that Adam Lanza, the Connecticut school massacre shooter, attempted to buy a gun at Dick's Sporting Goods in Danbury on Tuesday -- but was unsuccessful, a law enforcement source said.

Employees at the store -- about 12 miles from Sandy Hook Elementary -- have been interviewed and have searched the store's surveillance cameras for evidence that Adam Lanza had been there.