Connecticut Police reveal the discovery of special spreadsheet that suggests Adam Lanza spent years preparing for the heinous crime he committed on Dec. 14, 2012.

According to a report, investigators working the Lanza case discovered a "7 foot long, 4 foot wide spreadsheet with names, body counts and weapons from previous mass murders and even attempted killings." 

Police say the work that went into the spreadsheet was as obsessive as it was extensive, and that it shows Lanza spent his time thinking about ways people had been killed and could be killed, given a soft target where the killer had time to do as he pleased.

An anonymous law enforcement official said the more investigators looked at the spreadsheet, the more they saw that it was actually a score sheet in a game Lanza planned to win. To that end, they believe "he picked an elementary school [for his crime] because he believed it was a point of least resistance."   

Coupled with the spreadsheet, investigators found photos of Lanza from two years ago, strapped with weapons and striking death poses. In one photo, he held a gun to his own head. Said the law enforcement official: "You have to understand..he had this laid out for years before."

Said the official: "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." Instead, "he had been planning this thing forever."