Photos from the Newtown school shooting report

A yearlong investigation into the Newtown school shooting has provided disturbing insights into the gunman who killed his mother and then massacred 26 other people, but it still has not provided a motive.

Prosecutors closed the case Monday on the Sandy Hook Elementary shooting last December. Their report offered a chilling portrait of 20-year-old Adam Lanza as a loner who was obsessed with violence and bound by ritualistic behavior.

But they were unable to answer the question that everyone has been asking since the tragedy: Why? (AP)