New theories and details about what motivated 20-year-old Adam Lanza to carry out one of the nation's worst massacres are being reported in advance of a PBS report on Lanza set to air Tuesday, though Connecticut police have been careful to caution against drawing firm conclusions.

New details emerge about Sandy Hook shooter Adam Lanza

(Mahala Gaylord/Denver Post)New theories, details emergeAdam Lanza (via NBC News)Unnamed law enforcement sources cited in a CBS report Monday say Lanza "saw himself as being in direct competition with Anders Breivik, a Norweigan man who killed 77 people in July 2011." At 10 p.m. Tuesday, PBS' Frontline will air a special report produced in collaboration with Hartford Courant journalists as part of the weeklong "After Newtown" series. Detectives are also looking into the roles violent video games and Lanza's experiences ...

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