UPDATE 4:45 p.m.:
Authorities are reporting that the killer, armed with two handguns, committed suicide at the school and another person was found dead at a second scene, bringing the toll to 28.
Police shed no light on the motive for the attack.
UPDATE 3:50 p.m.:
The gunman drove to the school in his mother's car, the second official said. Three guns were found — a Glock and a Sig Sauer, both pistols, inside the school, and a .223-caliber rifle in the back of a car.
Adam Lanza's girlfriend and another friend were missing in New Jersey, the official also said.
UPDATE 3:15 p.m.:
A law enforcement official says the suspect in the Connecticut school shootings is 20-year-old Adam Lanza, the son of a teacher at the school where the shootings occurred. A second law enforcement official says the boy's mother, Nancy Lanza, is presumed dead.
The first official says Adam Lanza's older brother, 24-year-old Ryan, of Hoboken, N.J., is being questioned by police. An earlier report from a law enforcement official mistakenly transposed the brothers' first names.
Both officials spoke on the condition of anonymity because they were not authorized to speak on the record about the developing criminal investigation.
The first official said Adam Lanza is dead from a self-inflicted gunshot wound.
UPDATE 3 p.m.:
Police say 27 people were killed in the shooting at a Connecticut elementary school, including the gunman, and one person died at another scene.
The dead at the school include 20 children.
The gunman opened fire Friday morning inside a school where his mother worked. He blasted his way through the building as young students cowered helplessly in classrooms while their teachers and classmates were shot.
The gunman killed himself. Gov. Dannel P. Malloy says someone who lived with him also died.
Young students crying and looking frightened were escorted by adults through a parking lot in a line after the shots rang out in Newtown, 60 miles northeast of New York City.
UPDATE 2:20 p.m.:
A federal law enforcement official told The Wall Street Journal that a .223 Bushmaster rifle was found in the back of a vehicle at the scene. Two firearms were recovered near the alleged gunman’s body: a Glock and a Sig Sauer, both handguns.
UPDATE 2 p.m.:
The Associated Press reported that the gunman opened fire inside the Connecticut elementary school where his mother worked Friday, killing 26 people, including 18 children. The suspect's younger brother is being held.
The death toll — 26 victims plus the gunman — was given to The Associated Press by an official who spoke on condition of anonymity because the investigation was still under way.
Original story from The Associated Press
A gunman opened fire inside a Connecticut elementary school Friday in a shooting that left 27 people dead, including 20 children, an official said.
The official spoke on condition of anonymity because the investigation was still under way.
The shooting appeared to be the nation's second-deadliest school shooting, exceeded only by the Virginia Tech massacre in 2007.
Parents flooded to Sandy Hook Elementary School, about 60 miles northeast of New York City, looking for their children in the wake of the shooting. Students were told to close their eyes by police as they were led from the building.
A photo taken by The Newtown Bee newspaper showed a group of young students — some crying, others looking visibly frightened — being escorted by adults through a parking lot in a line, hands on each other's shoulders.
Students and staff were among the victims, state police Lt. Paul Vance said a brief news conference. He also said the gunman was dead inside the school, but he refused to say how people were killed.
Another official, speaking on condition of anonymity because the investigation was still under way, said the gunman apparently had two guns.
A law enforcement official in Washington said the attacker was a 20-year-old man with ties to the school and that one of the guns was a .223-caliber rifle. The official also said that police were searching a location in New Jersey in connection with the shootings. That official spoke on the condition of anonymity because the source was not authorized to speak on the record about the developing criminal investigation.
Stephen Delgiadice said his 8-year-old daughter heard two big bangs and teachers told her to get in a corner. His daughter was fine.
"It's alarming, especially in Newtown, Connecticut, which we always thought was the safest place in America," he said.
A dispatcher at the Newtown Volunteer Ambulance Corps said a teacher had been shot in the foot and taken to Danbury Hospital. Andrea Rynn, a spokeswoman at the hospital, said it had three patients from the school but she did not have information on the extent or nature of their injuries.
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.
"There's no words," Wilford said. "It's sheer terror, a sense of imminent danger, to get to your child and be there to protect him."
The White House said Barack Obama was notified of the shooting and his spokesman Jay Carney said the president had "enormous sympathy for families that are affected."