Sandy Hook shooter Adam Lanza was obsessed with mass murders and guns, authorities say.

Authorities believe Lanza corrected a spurt of posts on Wikipedia entries about mass killers. Lanza also posted about firearms on gun message boards.

At seventeen, Lanza, the Newtown gunman, wrote about having a "fetish for" .32 ACP bullets. The posts were made between April 2009 and February 2010.

Some posts discuss Connecticut gun laws and rifle recommendations. They reveal an obsession with weapons, violence, and mass murder.

Lanxa killed 20 children; six adults; his mother, Nancy; and himself at Sandy Hook Elementary school in Newtown, Connecticut in December 2012. The incident was the school shooting with the highest number of fatalities in American history.

Lanza is likely behind the "obsessive" editing of a dozen Wikipedia entries about mass shootings. Many were cases that bear a striking resemblance to Lanza's own shooting at Sandy Hook.

In one entry Lanza updated, Richard Farley killed seven people at a manufacturing company in Sunnyvale, California. Farley and Lanza both strapped hundreds of rounds of ammunition onto a vest and wore earplugs.

Lanza also edited articles about Anders Breivik, who killed 77 people in 2011 in Norway; and shootings at the Sello Mall near Helsinki, Finland; the Omaha, Nebraska Westroads mall shooting in 2007; and the ESL Inc. Massacre in 1988.

One post on a gun control forum questions whether a ban on semiautomatic pistols will be extended in Connecticut. Users say he should contact the police. Lanza responded, "I always prefer asking through proxy when I can avoid speaking to someone directly. I was just wondering if anyone knew because I have a fetish for .32 ACP."

Lanza used two semiautomatic pistols in his shooting. at Sandy Hook They were a Glock and Sig Sauer that belonged to his mother, a teacher.