The 20-year-old man behind the mass shooting in Newtown, Connecticut kept a database and "score sheet" of similar crimes as part of a plan to achieve greater levels of violence, CBS News reported on Monday.
Police said Adam Lanza, who killed 26 people in the December 2012 attack on Sandy Hook Elementary, had compiled information on several mass killings, and chose the school because he thought it was a convenient target.
One particular influence on Lanza's rampage was the July 2011 attack by Anders Breivik in Norway. Breivik, an avid fan of Islamophobic conservatives, killed 77 people in attacks in downtown Oslo and at a summer camp on nearby Utoya Island.
The New York Daily News reported on Sunday that Lanza's database contained the names of 500 gunmen and failed shooters, according to an anonymous officer who said he was briefed in detail on Lanza's plan at a law enforcement conference in a seminar by Connecticut State Police Col. Danny Stebbins.
Lanza's dossier, the source said, contained "names and the number of people killed and the weapons that were used, even the precise make and model of the weapons. It had to have taken years. It sounded like a doctoral thesis, that was the quality of the research."
But according to a Connecticut newspaper, the Torrington Register Citizen, the Daily News' report defied a request by Stebbins to not share his findings with the public before they could be delivered to the families of the victims in the Newtown shooting.
"It is unfortunate that someone in attendance chose not to honor Col. Stebbins' request to respect the families' right to know specifics of the investigation first," a state police spokesperson, Lt. J. Paul Vance, told the newspaper in a statement. "Law enforcement sensitive information was discussed dealing with tactical operational approaches by first responders on the day of the shootings."
Newtown First Selectman Pat Llodra, the town's chief executive, said he was not aware of any new efforts to share information on the shootings.
State police have said in the past they would release a report on their findings regarding the shooting once their investigators had completed their analysis. Vance did not comment on the specifics of the Daily News report.
On Monday, the Daily News reported that some lawmakers are also calling for increased monitoring of the video game industry after it was discovered that Lanza shared Breivik's affinity for playing violent games like the Call of Duty series.
"There are too many video games that celebrate the mass killing of innocent people," said Sen. Chuck Grassley (R-IA). "Games that despite attempts at industry self-regulation find their way into the hands of children."
Meanwhile, Sen. Jay Rockefeller (D-WV) has proposed granting the Federal Communication Commission more leeway in regulating video games.
"In today"s world, where kids can access content across a variety of devices often without parental supervision, it is unrealistic to assume that overworked and stressed parents can prevent their kids from viewing inappropriate content," said Rockefeller, who chairs the Senate Commerce Committee.
Watch CBS News' report on Lanza's grisly research, aired Monday, below.