The shooter also killed himself inside the school, authorities said, and his mother was later found dead at her home 2 miles away, www.courant.com reports.

The shootings took place in two first-grade classrooms around 9:30 a.m., sources said, and one witness said she believed as many as 100 rounds had been fired. All of the adults and 18 of the children were pronounced dead at the school. Two more students died at a hospital. A single victim was injured but not killed.

State police sources identified the shooter as Adam Lanza, 20. When Lanza was found - dead in a hallway of a self-inflicted gunshot wound - he was carrying his brother Ryan Lanza's identification, which initially led to confusion about his identity, police said.

Adam Lanza was dressed in black fatigues and brought two weapons into the school, police sources said: a Glock and a Sig Sauer, both pistols. A .223-caliber rifle was found in his car in the school parking lot, sources said.

Principal Dawn Hochsprung, 47, was among those killed."She died protecting the children that she adored so much. It's just incredibly shocking,'' said Gerald Stomski, first selectman in Woodbury, where Hochsprung lived. Hochsprung had been the principal in the Bethlehem and Woodbury school district before taking the job in Newtown two years ago.
Police have not confirmed the identities of the other victims, but they are believed to include a school psychologist and at least one teacher. Sandy Hook has more than 600 students from kindergarten through fourth grade.

As news of the massacre spread through the typically quiet Fairfield County town, panicked parents clogged roads as they streamed to the school in search of their young sons and daughters. Police evacuated the children to a nearby firehouse, and tearful parents were led into the building. Most came out relieved, clutching and caressing their children. A few came out empty-handed and grief-stricken.

Later in the day, authorities set up a makeshift morgue in the school and took photographs of the young victims to show to parents to make a positive identification.

The horror of the shooting reverberated far beyond the school. Impromptu vigils were held across the state. In Washington, D.C., House Speaker John Boehner ordered flags at the Capitol to be flown at half-staff. And at the White House, a visibly emotional President Barack Obama offered the nation's condolences. "Our hearts are broken today," he said. "This evening, Michelle and I will ... hug our children a little tighter and tell them that we love them," Obama said. "But there are families in Connecticut who cannot do that tonight."

Vanessa Bajraliu, a 9-year-old fourth grader, heard the shots. "I saw policemen - lots of policemen in the hallway with guns," she said. "The police took us out of the school. We were told to hold each others' hands and to close our eyes. We opened our eyes when we were outside."

Her brother, Mergim Bajraliu, 17, a senior at Newtown High School, was at his nearby home when he heard shots, he said. He went to a neighbor's house. "Then we heard sirens," he said. He rushed to the school on foot and saw a girl being carried out, he said. She looked badly injured. Another girl had blood on her face, he said.

Bajraliu soon found his sister and took her away from the scene. Parent Richard Wilford said his Sandy Hook second-grader, Richie, heard what he described as "pans falling" when gunshots rang out. He said that his son told him that his teacher went to check on the noise, then returned to the classroom, locked the door and told the students to stand in the corner.