Lanza removed the hard drive from his computer and damaged it prior to the shooting , creating a challenge for investigators to recover data . At the time of publication of the final report , it had not been possible to recover data from it . Police believe that Lanza extensively researched earlier mass shootings , including the 2011 Norway attacks and the 2006 West Nickel Mines School shooting at a one-room school in Nickel Mines , Pennsylvania . Police found that Lanza had downloaded videos relating to the Columbine High School massacre , other shootings and two videos of suicide by gunshot
Columbine High School massacre
Columbine High School massacre
Sandy Hook Elementary School shooting