Investigators on Saturday worked to understand what led a bright but painfully awkward 20-year-old to slaughter 26 children and adults at a Connecticut elementary school, while townspeople took down Christmas decorations and struggled with how to get through a holiday season that has suddenly become a time of mourning.

The tragedy spurred soul-searching and grief around the globe. Families as far away as Puerto Rico began to plan funerals for victims who still had their baby teeth, world leaders extended condolences, and vigils were held around the U.S.

Amid the sorrow, stories of heroism emerged, including an account of the Sandy Hook Elementary School principal who lost her life lunging at the gunman, Adam Lanza, in an attempt to overpower him.

Police shed no light on the motive for the second-deadliest school shooting in U.S. history, though state police Lt. Paul Vance said investigators had found “very good evidence … that our investigators will be able to use in painting the complete picture, the how and, more importantly, the why.” He would not elaborate.

However, another law enforcement official, speaking on condition of anonymity, said investigators have found no note or manifesto of the sort they have come to expect after murderous rampages such as the Virginia Tech bloodbath in 2007 that left 33 people dead.