Kaitlin Roig-Debellis who was in charge of 15 primary school aged children the day a gunman opened fire at Sandy Hook Elementary School in Connecticut on 14 December 2012 says she can never move on from that event, but must move forward.
During his rampage, Adam Lanza killed 20 children and six adult staff members, before turning the gun on himself.
Prior to the school massacre the 20-year-old had shot and killed his mother.
The incident was the deadliest mass shooting at a high school or primary school in US history and the second-deadliest mass shooting by a single person in US history, this after the 2007 Virginia Tech shootings
Sandy Hook teacher, Kaitlin Roig-Debellis, shielded her entire class of children aged six and seven by hiding them in a bathroom.
"When the shooting began and the killer stalked down the hallway toward our classroom, I stuffed my frantic students into a bathroom that was too tiny for one adult and told them to stay perfectly quiet. I was certain we were going to die," she said.
She has written about the experience and trying to recover from the trauma, in her memoir, Choosing Hope.
"To this day, I believe the killer came into our classroom, which was the first one in the hallway and, thinking it was empty, moved to the next classroom, and the next, shooting everyone he saw."
"I live every day wishing I could go back to December 13, back to who I was, who my kids were," said Ms Roig-DeBellis.
Since the masscare, Kaitlin Roig-DeBellis has founded Classes 4 Classes, which has built a social networking tool to help teach children - caring, kindness, empathy and consideration.