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A shooting at a Connecticut elementary school has left 27 people dead, including 20 children, six adults, and the shooter.

The shooter entered Sandy Hook Elementary School in Newtown, about 60 miles northeast of New York City, and opened fire in one section of the school leaving 18 children and six adults dead. Two other children were transported to a hospital where they later died of their injuries.

A law enforcement official in Washington said the attacker, who was killed at the scene, was a 20-year-old man named Adam Lanza, whose mother was a teacher at the school and was one of the adults killed. His Ryan Lanza, of Hoboken, N.J., is still be being questioned but is not in custody and is not believed to have any connection to the school killings.

The official says Ryan Lanza's computers and phone records were being searched but only "in an abundance of caution." He says Ryan told authorities he had not been in touch with his brother in recent years.

Lanza's father is alive but Adam's girlfriend is missing, according to authorities.

Authorities are investigating Lanza's Hoboken, N.J., home.

WATCH: Obama Gives Emotional Statement on Shooting

The town is more than 90 percent white and five percent Latino, according to the U.S. Census.

The shooting is the latest mass violent incident in a year that in recent days saw a deadly mall shooting in Oregon, and months ago a gunman opened fire in a suburban Colorado movie theater that killed about a dozen. Both gunmen are in their 20's. The Oregon shooter killed himself after killing two other people.

State police say Newtown police called them around 9:40 a.m. A SWAT team was among the throngs of police to respond.

Speaking at a brief conference, Connecticut state police said that the shooter is deceased and remains inside the school.

"The scene is secure, the situation is secure," said Connecticut State Police Lt. Paul Vance. "The public is not in danger."

Photos from the scene showed 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.

President Obama was notified around 10:30 in the morning.

"I would rather not relay reactions at this point because I don't have any confirmation to give to you about exactly what has happened or potential victims," said White House Press Secreatry Jay Carney. "The president is a father... he feel's enormous sympathy for families that are affected and to do everything we can to support state and local law enforcement and those enduring what appears to be very tragic event."

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."

Based on reporting by The Associated Press.

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