Sandy Hook Elementary School killer Adam Lanza had kept a spreadsheet with research on 400 mass murderers before his own notorious shooting crime.
As the Hartford Courant has revealed in a shocking article just days before the six-year anniversary of the massacre on Dec. 14, 2012, Lanza was obsessed with the details of serial killers.
Lanza, 20, gunned down gunned down and killed 20 children and six educators at the school in Newton, Connecticut, before committing suicide.
According to the Courant, who obtained the new material from Lanza's home, he began researching his extremely detailed list in 2006, six years before his own mass shooting.
Lanza kept 17 categories on his spreadsheet, including the names of the killers, the number of people they killed, the weapons used, the date, time, and place of the murders, and what happened to the various murderers.
Incredibly, Lanza's list began with murderers from 1786.
It ended in 2010.
The spreadsheet included such killers as George Sodini, who killed three people in a Pittsburgh gym before shooting himself dead in 2009.
Lanza's final entry was about Derrick Bird, who murdered 12 in Cumbria, England.
Lanza also made his own corrections to mass shooters' Wikipedia pages, the news site has reported.
The troubled young man, whose bone-chilling crime caused a new debate about gun rights in America, wrote in a chatroom before going on his rampage, "Compared to the legions of people who focus solely on serial killers, it's almost impossible to find anyone who's interested in mass murderers so I thought that I might as well introduce myself.
"I've been researching this topic since 2006 and I started compiling a formal list at the beginning of 2010."
Lanza lost interest in keeping the spreadsheet before committing his own murders.
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