Undisclosed law enforcement sources told CBS News on Monday that Adam Lanza shot children at Sandy Hook Elementary School in Connecticut after being inspired by Norwegian mass murderer Anders Breivik.

Lanza thought he was in competition with Breivik, a rightwing extremist who killed 77 people in 2011. Breivik said he was protecting his country from multiculturalism by setting off a car bomb at government offices before gunning down 69 people at a Labour Party youth camp.

Sources also told CBS News that Lanza was motivated by violent video games and viewed killing others as a type of "score." Lanza apparently decided to kill 26 people, including 20 young children, at Sandy Hook in December because the school was an easy target.

"This doesn't surprise me at all," criminologist James Fox said on CNN. "When the question was raised why did he go to that school, the clear answer always was he knew when he got there there would be a lot of victims under his gun, and he could hurt society in a most profound way. Where else could he go where so many people would be congregated?"

Fox also condemned the media for portraying mass shootings as "record breaking," saying it encouraged people like Lanza. He warned the media sometimes "crossed the line" when covering mass shootings, placing too much emphasis on the perpetrator and not enough on the crime itself.

Connecticut State Police said it had not concluded its investigation of the shooting and descriptions of Lanza's motives were "mere speculation."

Watch video, uploaded to YouTube by CNN, below: