When Adam Lanza stormed into Victoria Soto's first-grade classroom, he was armed with semi-automatic weapons with which he had already killed 20 small children. She had only her courage, and her instinct to protect her class.

Ms Soto, 27, faced the killer, and saved her children. Accounts of what happened differ. One, posted on Tumblr by a friend, says that she had bundled the class into a large closet, and told the gunman that they had gone to the gym. Another says she was found huddled over the children. Either way, Lanza shot her, and then turned the gun on himself. Her cousin, Jim Wiltsie, told ABC News: "I'm just proud that Vicki had the instincts to protect her kids from harm. It brings peace to know that Vicki was doing what she loved, protecting the children, and in our eyes she's a hero."

She is not the only one. If anybody wanted to know the kind of people who become teachers, they need only read of the bravery of the staff at Sandy Hook Elementary School. It starts with the principal, Dawn Hochsprung, who had the presence of mind to turn on the school intercom, broadcasting screaming and gunshots into every classroom, so that others had to time to take cover. "That saved a lot of people," said one teacher Theodore Varga, who survived the massacre.

Ms Hochsprung was in a meeting with a parent and senior staff when Lanza began shooting nearby. At the sound of gunshots and screaming, some in her office dived for cover, but Ms Hochsprung and the school's psychologist, Mary Sherlach, 56, ran out to confront Lanza, shouting back to the others to lock the door. They were both shot dead, Ms Hochsprung as she lunged at the killer.

Ms Sherlach was preparing to retire, having helped hundreds of students go through family break-ups, bullying and events that – until Friday – had been the toughest moments of their young lives. While others hid, she and the principal ran towards the danger. The school therapist Diane Day, who was in the meeting, said: "They didn't think twice about confronting [him] or seeing what was going on." Without a lock to secure the door, another teacher at the meeting used her body to hold it shut, and was shot in the leg and arm through the door.

Maryrose Kristopik, a music teacher at the school, kept 20 children safe by barricading them into a closet. Even when the gunman battered on the door screaming: "Let me in! Let me in!" she kept her nerve and blocked the door with her own body. Mrs Kristopik said: "I did take the children into the closet and talked with them to keep them quiet. I told them that I loved them. I said there was a bad person in the school. I didn't want to tell them anything past that."

One door had several instruments, including big xylophones, blocking it and she stood in front of the other holding it firm. "I was just trying to be as strong as possible," she said. "I was thinking about the children. I told them that we had to keep quiet and we were hiding and nobody knew we were there. Of course I was afraid too. I wanted them to be quiet, I thought it was a pretty secure, out-of-the-way place." She led her children out only when she heard the gunshots had stopped. Brenda Lebinski said her eight-year-old daughter was safe thanks to the teacher's actions. "My daughter's teacher is my hero," Ms Lebinski said. "She locked all the kids in a closet and that saved their lives."

Large windows left teacher Kaitlin Roig's classroom exposed, so she huddled 15 children into a tiny bathroom when she first heard gunshots. The 29-year-old locked the door and pulled a bookshelf across it. She said it was a struggle to get all the pupils in but she knew it was their only option. "I put one of my students on top of the toilet. I just knew we had to get in there. I was just telling them they were going to be OK," she told ABC News. "I told them we had to be absolutely quiet because I was afraid that if he did come in and hear us he would just shoot at the door. I said there are bad guys out there now. We need to wait for the good guys."

Thinking these might be their last moments alive, she assumed the role of a parent. "I said, 'I need you to know that I love you all very much and it's going to be OK'. Because I thought we were all going to die. I wanted them to know someone loved them and I wanted that to be the last thing they heard." When the police arrived to tell them it was safe to come out, Ms Roig was so frightened she made them put their badges under the door so she could be sure it was them. Only then did she lead the children out to safety.

Another teacher, Abbey Clements, acted quickly to save lives. When she heard gunshots outside her classroom she initially thought they might be folding chairs, left out for a concert, falling over. But when she looked outside she was confronted with a very different scene. "When I poked my head out the door and saw the custodian [janitor] running to the front of the building I realised they were shots," she said. She pulled two students and two other teachers who were standing in the hall through her door to hide them. "We corralled those two kids into my classroom to stay with me. We went into lockdown, which meant that I ran to get the keys and told the kids to sit in the place where we practised for emergencies.

"It was even scary to lock the door because I had to open the door back up and put my hand out – because the lock is on the outside – and then come back into the closet area," Ms Clements added. Trying to calm the children, she attempted to muffle the haunting sounds of gunshots and screams broadcasting over the intercom and read them stories.

An as-yet-unidentified teacher saved an eight-year-old pupil. He was standing in a hallway as bullets whistled through when he was pulled from harm. "I saw some of the bullets going down the hall that I was right next to and then a teacher pulled me into her classroom," the boy told CBS News.

It was not just teachers who showed extraordinary courage. While the gunman roamed the halls, the school janitor – whose fate is still not known – ran along corridors shouting "Guys! Get down! Hide!", checking that classroom doors were locked. And librarian Yvonne Cech locked herself, two library clerks, an assistant and 18 fourth-graders in a closet behind the library's filing cabinets while the sound of gunfire cracked outside.

But there were 20 children the staff could not save. Their names and lives could be those from any primary school on either side of the Atlantic. Among them are Daniel Barden, aged six; Chase Kowalski, whose sister Natalie attends the school but escaped injury; Jesse Lewis, six, whose class were set to make gingerbread houses that day; Grace McDonnell, aged six, who lived a street away from her killer; Ana Marquez-Greene, aged seven, the daughter of Canadian jazz saxophonist Jimmy Greene; Emilie Parker, aged six, whose family had moved to Newtown from Utah only a year ago; Avielle Richman, Catherine Hubbard, Noah Vabner, and Benjamin Wheeler, all aged six.

When parents rushed to the nearby fire station that was being used as an emergency base, these were among the children who would not be clutched by grateful families.

Monsignor Robert Weiss of Newtown's St Rose of Lima Catholic church was there. He watched as parents came to realise that they would never see their children alive again. "All of them were hoping their child would be found OK. But when they gave out the actual death toll, they realised their child was gone," Mgr Weiss said.

He recalled the reaction of one of the victims' brothers. "They told a little boy it was his sister who passed on," Mgr Weiss said. "The boy's response was, 'I'm not going to have anyone to play with.'"

Additional reporting by Paul Bignell, Rachel Bradley, Nabeelah Jaffer, Sanchez Manning, Sara Spary, Judith Welikala and Angus Handley

The victims

Victoria Soto

Victoria's cousin, Jim Wiltsie, a police officer, said the 27‑year‑old died trying to shield her pupils. "I'm just proud that Vicki had the instincts to protect her kids from harm," he said. "It brings peace to know that Vicki was doing what she loved, protecting the children, and in our eyes she's a hero."

Emilie Parker

Six-year-old Emilie's parents Robbie and Alissa moved their family from Ogden, Utah, last year after Emilie's father, a physician's assistant, found work in the Newtown area. Brad Schultz, a family friend, said Emilie's body is to be buried in Ogden.

Avielle Richman

Avielle started first grade at Sandy Hook last August. Her mother Jennifer, whose company sells electrical equipment, attended the same school as a child.

Mary Sherlach

The school psychologist's son-in law said: "It was going to be her last year. She loved her job. She's done this for her whole career. She wanted to help kids get over their problems and go on to be successful."

Dawn Hochsprung

The school principal's niece, MaryAnn Suarez of Naugatuck, said her aunt devoted her life to schoolchildren. "In every school she worked at, every teacher was her friend. She was every child's friend."

Ana Marquez-Greene

The six-year-old daughter of Canadian jazz saxophonist Jimmy Greene. Her brother Isaiah, who also attended the school, escaped unharmed.

Lauren Rousseau

The 30-year-old teacher had just landed her first permanent job as a teacher at Sandy Hook after several years as a substitute teacher. Was due to go out with her boyfriend to the cinema before she was shot.

Jesse Lewis

His father, Neil Heslin, said: "I dropped him off at school at 9am. He went happily. That was the last I saw of him." Mr Heslin said his six-year-old son had planned to make gingerbread houses in class.

Daniel Barden

Known to friends as "Mini" Barden. His elder brother's football coach confirmed Daniel was among the victims at the school.

Timeline

9.00 Adam Lanza shoots dead his mother, Nancy, with one of her handguns.

9.15 Lanza leaves his mother's home in her car, armed with two of her handguns, a Sig Sauer and Glock 9mm, and one Bushmaster .223 calibre rifle.

9.30 Arriving at Sandy Hook Elementary School, Lanza forces his way in through a security door.

9.35 He opens fire inside the school. Dawn Hochsprung, the principal, is among the first to be killed after emerging to confront him. Before she died, she switched on the school's intercom system, alerting the rest of the building. The school psychologist, Mary Sherlach, was also shot dead.

9.36 Police patrols are alerted to the shootings. A janitor runs through corridors warning teachers a gunman is on the loose and locking doors.

9.38 Lanza enters two classrooms, killing 20 children aged from five to 10 and seven adults. Only one wounded child survives. Lanza kills the first-grade teacher Victoria Soto as she attempts to protect her class, then turns the gun on himself. Throughout the rampage he does not speak a single word.

9.40 Police officers move through the building searching for the gunman.

9.46 Police officer at the scene radios back: "I've got bodies here. Need ambulances."

14.15 Body of the gunman's mother, Nancy Lanza, is found in her home on Yogananda Street, Newtown.

14.50 Gunman erroneously named as Ryan Lanza, 24.