A 16-year-old who attacked Silver Rail Elementary School on Thursday carried a pump-action shotgun his mother had bought. Coverage said that sale met existing purchase rules at the counter. CNN reported he had fired several kinds of shotgun shells and still had about 44 unused rounds when a father of two pupils at the school stopped him by shooting him. Authorities treat a lawful transfer as one that cleared background screening and related point-of-sale limits. The account added that most widely covered public attackers obtained guns after those same checks.