boxing day 2012: 'Let me in! Let me in!' Hero music teacher saved 15 children by barricading them into a closet while gunman Adam Lanza hammered on door

Maryrose Kristopik saved 15 children during the shooting at Sandy Hook by barricading them into a closet

Gunman Adam Lanza, 20, was outside the door begging to be let in

Parents have hailed Kristopik as a hero for her bravery

PUBLISHED: 15:54 EST, 14 December 2012 | UPDATED: 16:35 EST, 14 December 2012

A music teacher managed to save 15 children during Friday's shooting massacre at Sandy Hook Elementary School in Connecticut by barricading them into a closet, while gunman Adam Lanza, 20, stood outside screaming 'Let me in! Let me in!'

Maryrose Kristopik has been hailed a 'hero' by parents after herding the children to safety in a closet and barricading the door to prevent Lanza from entering.

An unnamed mother, in her 40s, whose nine-year-old son was among the children said: 'I want to thank her. She saved their lives.

A mother hugs her daughter following a shooting at the Sandy Hook Elementary School, Conn., on Friday

Sandy Hook Elementary School: Reports state that 27 people are dead, including 14 children

'The shooter kept banging on the door screaming: "Let me in! Let me in!" but he didn't get in.

'Now I have to explain to my nine-year-old son that his friends won't be coming back. How am I supposed to do that?'

Brenda Lebinski said her eight-year-old daughter is safe thanks to the teacher's decision to move all kids into a closet when a gunman had entered the building.

'My daughter's teacher is my hero,' Lebinski said. 'She locked all the kids in a closet and that saved their lives.'

Alberta Bajraliu 41, got a call from a friend who heard a gunshot at the school and told her to check it out.

Mrs Alberta's nine-year-old daughter Venesa was at the school but her two other children are not.

She said: 'I was one of the first there and they were bringing children out, carrying them out. One girl came out and her face was covered in blood and she had bits of meat from other people in her hair. It was terrible.

'Another girl just looked shocked. They brought one girl out and I thought it was my daughter. They asked me: 'Does she have black trousers?' and I said no as Venesa had jeans.

A woman waits to hear about her sister, a teacher, following the shooting at the Sandy Hook Elementary School in Newtown

A group of young students - some crying, others looking visibly frightened - were escorted by adults through a parking lot in a line, hands on each other's shoulders

'When I saw her I just felt so relieved. She has not spoken much about what happened. She said she was in an art class and the teacher closed the door and they were waiting until they could get out.

Miss Bajraliu also paid tribute to the school's principal Dawn Hochsprung who is believed to have been killed. She said: 'She would have done anything for her children'.

Josh Milas, 21, a former pupil at the school, also paid tribute to her and said: 'She loved those kids. She was a great person'.

Lanza opened fire inside the Connecticut elementary school where his mother worked Friday, killing 26 people, including 18 children, and forcing students to cower in classrooms and then flee with the help of teachers and police.

The massacre is the nation's second-deadliest school shooting, exceeded only by the Virginia Tech massacre in 2007, which left 32 people and the gunman dead.

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 many people were killed.

Third grade school children at Sandy Hook Elementary School, about 60 miles northeast of New York City

The massacre is the nation's second-deadliest school shooting, exceeded only by the Virginia Tech massacre in 2007

A law enforcement official briefed on the shooting said the gunman died from a self-inflicted gunshot wound and that one of the victims was the man's mother, a teacher. The official wasn't authorized to speak about the investigation.

The attacker was a 20-year-old man armed with a .223-caliber rifle.

Robert Licata said his six-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 eight-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.

Danbury Hospital was the only hospital to take in victims from the shootings, admitting three patients. Doctors said at a news conference they cleared four trauma rooms to treat shooting victims.

A man and woman leave the staging area for family around near the scene of a shooting at the Sandy Hook Elementary School

People embrace at a firehouse staging area for family around near the scene of a shooting at the Sandy Hook Elementary School in Newtown

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 seven-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. Then the gym teachers immediately gathered the children in a corner and kept them safe in a corner,' Makris said.

The fourth-grader told his mother that the students stayed huddled until police came in 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 policeman came in and helped them get out of the building and told them to run,' Makris said. 'And they ran to the firehouse.'

A HISTORY OF VIOLENCE: AMERICA'S WORST SCHOOL MASSACRES

1. Virginia Tech - 32 dead plus the shooter

16 April 2007, Blacksberg, Colorado

Student Seung Hui Cho, 23, killed two students in a dorm and then went through building of classrooms armed with two handguns, shooting at random before killing himself.

2. University of Texas - 16 dead plus shooter

1 August 1966, Austin, Texas

Former Marine sniper Charles Whitman, 25, armed with an arsenal of weapons shot victims from the observation deck of the campus tower.

3. Columbine High School - 13 dead plus two shooters

20 April 1999, Littleton, Colorado

Students Eric Harris, 18, and Dylan Klebold, 17, opened fire outside the school killing students and one teacher before shooting themselves in the library.

4. Red Lake High School - 9 dead plus shooter

21 March 2005, Red Lake, Minnesota

Jeffrey Weise, 17, goes on a shooting spree at Red Lake High School killing nine people, including his grandfather, before shooting himself.

5. University of Iowa - five dead plus shooter

1 November 1991, University of Iowa

Gang Lu, 27, a graduate student from China killed five with a .38-caliber revolver. He was apparently angry because his doctoral dissertation had not been nominated for an academic award.

6. Amish schoolhouse massacre - six dead plus shooter

2 October 2, 2006, Nickel Mines, Pennsylvania

Charles Carl Roberts IV, 32, executes five girls aged 7 to 13 before killing himself in a small Amish schoolhouse

7. Jonesboro, Arkansas - five dead

24 March 1998, Jonesboro, Arkansas

Mitchell Johnson, 10, and Andrew Golden, 8, took seven guns to school and pulled the fire alarm and shot students as they headed for the exits. Four died plus a teacher. The pair were sent to a juvenile detention center and released in 2005.

8. Cleveland Elementary School - five dead plus shooter

17 January 1989, in Stockton, California

Patrick Edward Purdy entered a schoolyard and opened fire with a semiautomatic rifle at Cleveland Elementary School. Five children died and 30 others were wounded including one teacher. He then shot himself.

9. University of Arizona – three dead plus shooter

28 October 2002, University of Arizona

Robert Flores, 40, a nursing student shot an instructor in her office before entering a classroom and killing two more teachers before committing suicide.

10. Kent State University – four dead

4 May 1970, Kent State University in Ohio

National Guard troops killed four students who took part in anti-war protests on the campus of Kent State University in Ohio.