Feb. 18, 2013 CBS News
Law enforcement sources say Adam Lanza was motivated by violent video games and a strong desire to kill more people than another infamous mass murderer.
Sources say Lanza saw himself as being in direct competition with Anders Breivik, a Norwegian man who killed 77 people in July 2011.
Breivik killed eight with a bombing in downtown Oslo. He then moved to a nearby island where hunted down and fatally shot 69 people, mostly teenagers attending a summer camp.
Two officials who have been briefed on the Newtown, Conn., investigation say Lanza wanted to top Breivik's death toll and targeted nearby Sandy Hook Elementary School because it was the "easiest target" with the "largest cluster of people."
Evidence shows that his mind, sources say, Lanza was also likely acting out the fantasies of a video game as he killed 20 first graders and six adults at the school. For Lanza, the deaths apparently amounted to some kind of "score."