Key facts from the scene of the shooting at the school in the US state of Connecticut:
The toll: 28 dead, including the gunman, Adam Lanza; his mother, Nancy Lanza; the elementary school's principal, Dawn Hochsprung; and 20 schoolchildren, as young as 5 years old. A woman who works at the school was wounded.
The suspect: 20-year-old Adam Lanza wore a pocket protector when he was in high school and was an honor student, and was called "remote" and "probably a genius" by classmates. A law enforcement official said he may have had a personality disorder. He grew up in an affluent neighborhood with neighbors who worked as executives at companies like IBM. Police said he forced his way into the school and that investigators had found "very good evidence" with hopes that it would answer questions about a motive.
The scene: Police told children to close their eyes as they led them past the carnage from their classrooms. The intercom broadcast screams; witnesses heard popping sounds, or, as a boy said, something that sounded like "cans falling." Crying children were escorted through the school's parking lot in line, hands on one another's shoulders, as panicked parents raced to the school. Witnesses said the shooter said nothing.
Where they died: Most of the dead were found in two classrooms; Lanza's mother, Nancy, was found dead at her home. The children killed were between ages 5 and 10.
Guns: A law enforcement official said a Glock and a Sig Sauer, both pistols, and a .223-caliber Bushmaster rifle were found in the school and a fourth weapon was found outside the school, and that investigators were going to shooting ranges and gun stores to see if Lanza had frequented them. The official was not authorized to discuss information with reporters and spoke on condition of anonymity.
The family: Lanza's mother was well-liked and was called a nurturing parent who enjoyed hosting dice games and preparing for the holidays. She divorced Peter Lanza, a tax director who lives in Stamford, Connecticut, four years ago. Lanza's 24-year-old brother, Ryan, works in Manhattan and was questioned by police near his New Jersey home but is not a suspect. Law enforcement officials initially identified him as the suspect.
The town: Idyllic, 300-year-old Newtown is a postcard New England town is home to garden clubs and Christmas tree lightings. The Spencer Tracy-Katharine Hepburn comedy Adam's Rib was filmed decades ago on a lake in the town, now a bedroom community of 27,000 where executives commute to Manhattan.
History: The shooting is the second-deadliest in U.S. history and one of the deadliest mass shootings around the world. A gunman at Virginia Tech University killed 33, including himself, in 2007. Only Virginia Tech and the mass killings of 77 in Norway in 2011 had greater death tolls across the world over the past 20 years.