Kaitlin Roig is one of many heroes that have been named in the aftermath of the Sandy Hook Elementary shootings.
Roig, a first grade teacher, ushered her students into the bathroom on Friday morning when the shooting began.
"Suddenly, I heard rapid fire... like an assault weapon. I knew something was wrong," Roig, 29, told "World News" anchor Diane Sawyer.
She secured the door shut with a storage unit and later refused to allow police into the room, insisting that they show proof of their authority.
"I didn't believe them," she told ABC News. "I told them if they were cops, they could get the key... They did and then unlocked the bathroom."
Even after locking herself and her students in a bathroom, Roig said that there was so much gunfire that she feared that her students would not survive.
"It was horrific," she said. "I didn't think we were going to live."
Despite her fears, Roig tried to comfort her students by telling them that she loved them and encouraged them to pray and "think happy thoughts."
"I thought we were all going to die," she told ABC. "I told the kids I love them and I was so happy they were my students... I said anyone who believed in the power of the prayer, we need to pray and those who don't believe in prayer" think happy thoughts."
She said the last thing that she wanted the children to hear was her voice telling them that it would be "ok."
Adam Lanza, 20, killed his mother at their home, which was a few blocks away from the school, before heading to Sandy Hook Elementary and opening fire. Within minutes he had killed 26 people and himself, 20 of them were children aged six to seven years old. Roig was amongst many heroes, who attempted to save children in the school. Other school administrators also locked their kids in closets; one allegedly lost her life after attempting to over power the shooter.