NEWTOWN, Conn. — A gunman opened fire inside a Connecticut elementary school Friday, killing 27 people, including at least 18 children, and forcing students to cower in classrooms and then flee with the help of teachers and police.

The death toll was given to The Associated Press by an official who 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 one another’s shoulders.

Students and staff were among the victims, state police Lt. Paul Vance said at a brief news conference. He also said the gunman was dead inside the school, but he refused to say how many people were killed.

Another official, speaking on condition of anonymity, 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 police were searching a location in New Jersey in connection with the shootings. That official was not authorized to speak on the record about the developing criminal investigation.

Robert Licata said his 6-year-old son was in class when the gunman burst in and shot the teacher.

“That’s when my son grabbed a bunch of his friends and ran out the door,” he said. “He was very brave. He waited for his friends.”

He said the shooter didn’t say a word.

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 the facility 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 added that 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.”

Melissa Makris, 43, said her 10-year-old son, Philip, was in the school gym.

“He said he heard a lot of loud noises and then screaming,” Makris said. “Then the gym teachers immediately gathered the children in a corner and kept them safe in a corner.”

The fourth-grader told his mother that the students stayed huddled until police came into the gym. He also told her that he saw what looked like a body under a blanket as he fled the school.

“He said the policemen came in and helped them get out of the building and told them to run,” Makris said. “And they ran to the firehouse.”

The White House said President Obama was notified of the shooting. Press secretary Jay Carney said the president had “enormous sympathy for families that are affected.”Jim Fitzgerald in Newtown, Pete Yost in Washington and Michael Melia in Hartford contributed to this report.