The Associated Press reports that 27 people, including 18 children, were killed on Friday morning in a school shooting at Sandy Hook Elementary in Newtown, Connecticut. Much remains unknown about the mass shooting, which is already being described as one of the worst in American history. But a picture of terror and tragedy is slowly emerging from news reports on the ground. Here, some details of the shooting as described by witnesses:
A student at the school told an NBC affiliate in Connecticut: "I was in the gym and I heard like seven loud booms, and the gym teachers told us to go in the corner and we huddled. We all heard these booming noises, and we started crying. So the gym teachers told us to go into the office where no one could find us. Then a police officer told us to run outside."
Mergim Bajraliu, 17, heard the gunshots echo from his home and raced to check on his 9-year-old sister at the school. He said his sister, who was fine, heard a scream come over the intercom at one point. He said teachers were shaking and crying as they came out of the building.
"Everyone was just traumatized," he said.
Richard Wilford's 7-year-old son, Richie, is in the second grade at the school. His son told him that he heard a noise that "sounded like what he described as cans falling."
The boy told him a teacher went out to check on the noise, came back in, locked the door and had the kids huddle up in the corner until police arrived.
Brenda Lebinski, whose 8-year-old daughter attends the school, was among the parents who raced to check on their children. "I saw her and it was the happiest moment of my life," she said.
Stephen Delgiadice said his 8-year-old daughter heard two big bangs and teachers told her to get in a corner. His daughter wasn't harmed. "It's alarming, especially in Newtown, Conn., which we always thought was the safest place in America," he said.
The mom who spoke to CNN's Meredith Artley said she heard "at least 100 rounds" being fired.
The shooting began about 9:35 a.m., the parent said. There was a "pop pop pop" in the hall outside the room. Three people went out of the room into the hall where the sounds had come from. "Only one person came back," we were told.
The witness told Artley that she then called 911. She said she never saw the shooter but she later was escorted outside the room past two bodies lying in blood.
A 9-year-old student heard the gunshots this morning.
"I saw police with big guns," said Venesa Bajraliu. "It was a little scary."
She said she was in her classroom when she heard shots, about 20. The class was instructed to go into the teacher's office, she said.
Police came and took the students out, telling them to close their eyes.
Eight-year-old Alexis Wasik, a third-grader at the school, said police were checking everybody inside the school before they were escorted to the firehouse.
"We had to walk with a partner," she said.
Lebinski said a mother who was at the school during the shooting told her a "masked man" entered the principal's office and may have shot the principal. Lebinski, who is friends with the mother who was at the school, said the principal was "severely injured."
The principal and school psychologist leaped out of their seats and ran out of the room, Ms. Day recalled. "They didn’t think twice about confronting or seeing what was going on," she said.
"At first we heard a bunch of kids scream, and then it was just quiet and all you could hear was the shooting," Ms. Day said.
Without a lock on the door, the school's lead teacher pressed her body against the door to hold it shut, Ms. Day said. That teacher was shot through the door in the leg and arm. "She was our hero," Ms. Day said.