Adam Lanza Planned Other Mass Murders

People close to the investigation tell The Associated Press that the gunman in the Connecticut school massacre showed interest in other mass killings.

Adam Lanza at an unspecified time and place from a 2008 yearbook (ABC News via Getty Images)

Twenty-year-old Adam Lanza killed his mother at their home before killing 20 first-graders and six staff members at Sandy Hook Elementary School in Newtown on Dec. 14. He killed himself as police arrived.

A law enforcement official briefed on the investigation says authorities found literature on other mass shootings at Adam Lanza's house.

Another person familiar with the investigation says Adam Lanza showed an interest in other mass murders. They spoke on condition of anonymity because the investigation is continuing.

A police report is expected around June. State police have declined to comment.

The Hartford Courant and the Hearst Connecticut Media Group first reported Wednesday that Lanza had done research on other mass killings.