By the time Adam Lanza massacred 26 children and adults at a Connecticut school two years ago, he was living in nearly complete isolation, communicating with no one except an online network of people obsessed with mass murder, a report released on Friday said.

The 20-year-old's fascination with violence, which came to a head in the December 2012 shootings at the Sandy Hook Elementary School in Newtown, was already evident when Lanza was in grade school, according to the state's Office of the Child Advocate.

As evidence, its report cites disturbing images that Lanza used to illustrate a story he wrote in which a raging grandmother shoots with a "rifle cane" and describes children playing a game of "hide and go die."