The purpose of this report is to identify the person or persons criminally responsible for the twenty-seven homicides that occurred in Newtown, Connecticut, on the morning of December 14, 2012, to determine what crimes were committed, and to indicate if there will be any state prosecutions as a result of the incident. Since December 14, 2012, the Connecticut State Police and the State’s Attorney’s Office have worked with the federal authorities sharing responsibilities for various aspects of this investigation. Numerous other municipal, state and federal agencies assisted in the investigation. The investigation materials reflect thousands of law enforcement and prosecutor hours. Apart from physical evidence, the materials consist of more than seven-hundred individual files that include reports, statements, interviews, videos, laboratory tests and results, photographs, diagrams, search warrants and returns, as well as evaluations of those items.