Spengler had armed himself with three guns : a .38-caliber revolver , a 12-gauge shotgun , and a .223-caliber Bushmaster semiautomatic rifle outfitted with a flash suppressor . Spengler had served 17 years in jail for manslaughter , having been convicted in 1981 of beating his 92-year-old grandmother to death with a hammer in 1980 . He shot and killed himself as a SWAT team approached . Later , human remains believed to be those of his elder sister , with whom he had feuded , were found in his house . On December 28 , 2012 , Dawn Nguyen , 24 , of Rochester , New York , was arrested and charged in connection with furnishing Spengler with certain weapons in his arsenal which were used in the ambush . She faces a state charge of filing a falsified business record . The New York State Senate subsequently included a " Webster provision " in a gun control law passed in the wake of the Sandy Hook Elementary School shooting , mandating life without parole for murderers of emergency personnel
Sandy Hook Elementary School shooting
Sandy Hook Elementary School shooting
Webster, New York