By Cole Hill (staff@latinospost.com) | First Posted: Mar 19, 2013 12:55 PM EDT

As the city of Newtown, Conn. continues to grieve in the wake of the Sandy Hook Elementary School shooting in December, new evidence has emerged indicating shooter Adam Lanza had planned the attack for years with a meticulous 'video game styled' spreadsheet. 

The morning of Dec. 14, 20-year-old Lanza shot his mother Nancy four times as she lay in bed, packed at least three of her guns, and then drove her car to the Connecticut K-4 elementary school. He opened fire in two classrooms around 9:30 a.m., fatally shooting 20 children and six adults, and then committed suicide. Police are still searching for a motive; witnesses said the shooter didn't utter a word. The attack was the second-deadliest shooting ever by a single gunman in U.S. history. 

The New York Daily News spoke to an unidentified "law enforcement veteran" who recently visited a conference where Connecticut State Police colonel Danny Stebbins spoke at length about the tragedy and revealed numerous new details surrounding the case. 

Stebbins reportedly explained that police now know Lanza had been planning the shooting at Sandy Hook for years with a 7 foot long, 4 foot wide spreadsheet that displayed obsessively researched information - in nine-point font - concerning "virtually every mass murder" in the U.S. and abroad.

"We were told (Lanza) had around 500 people on this sheet," the unidentified officer told the Daily News. "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."

Stebbins said police now believe Lanza thought of the mass shooting as an opportunity to win video game-like glory by racking up the highest amount of kills. They think he chose the elementary school because it would be a location with the least amount of resistance, and provide the easiest way to score "points."

"They don't believe this was just a spreadsheet. They believe it was a score sheet," the source continued. "This was the work of a video gamer, and that it was his intent to put his own name at the very top of that list." 

Police also now believe Adam Lanza's mother, Nancy, enabled her son's fascination with guns by making "straw purchases" for him. The three guns used in the shooting were legally purchased and registered to his mother. Lanza reportedly primarily used a military-style Bushmaster .223 assault rifle during the shootings.

Stebbins said that police found even more evidence beyond the spreadsheet that also indicates he was planning the attack for years. 

"He didn't snap that day, he wasn't one of those guys who was mad as hell and wasn't going to take it anymore," the source said. "He had been planning this thing forever. In the end, it was just a perfect storm: These guns, one of them an AR-15, in the hands of a violent, insane gamer. It was like porn to a rapist. They feed on it until they go out and say, enough of the video screen. Now I'm actually going to be a hunter."

There were 15 mass shootings in the U.S. in 2012 alone, according to The Huffington Post.

A 2011 Supreme Court decision upholding the right of minors to purchase violent video games in California ruled 7-2 that there is no conclusive causal connection between violent video games and violence.

"Psychological studies purporting to show a connection between exposure to violent video games and harmful effects on children do not prove  that such exposure causes minors to act aggressively. Any demonstrated effects are both small and indistinguishable from effects produced by other media...California also cannot show that the Act's restrictions meet the alleged substantial need of parents who wish to restrict their children's access to violent videos," the majority said in its opinion, according to the Washington Post.

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