Facing down a gunman, placing yourself in the path of flying bullets, forfeiting your life to protect innocents. It's a job description fitting for a soldier or police officer, but for a school teacher -- an elementary school teacher at that?

What the teachers and principal at Sandy Hook Elementary School did for the children in their care could win a soldier in a war zone a Purple Heart.

But the soldier makes a conscious choice to face mortal danger when he or she enlists. Sandy Hook's heroes did not.

Adam Lanza did not give them that choice when he opened fire in the hallway and two classrooms Friday in Newtown, Connecticut.

Long before it happened, Principal Dawn Hochsprung tried to prevent a shooting -- or any other calamity -- by implementing new security measures at Sandy Hook. She made sure teachers practiced getting into lockdown mode.

The front door was locked when the gunman arrived. A mother meeting with Hochsprung about her struggling child was astounded that the gunman had gotten in: "It's a locked school; you have to be buzzed in," she later said.

Lanza blasted his way in.

Hochsprung heard the loud pop. She, school psychologist Mary Sherlach and Vice Principal Natalie Hammond went to investigate.

They were acting as the first line of protection and paid heavily for it. Only Hammond returned from the hallway alive -- but not unscathed.

Along with Hochsprung, 47, and Sherlach, 56, four teachers perished.

Victoria Soto, 27, moved her first-grade students away from the classroom door. The gunman burst in and shot her, according to the father of a surviving student.

"She would not hesitate to think to save anyone else before herself and especially children," her mother, Donna Soto, told CNN's Piers Morgan.

Anne Marie Murphy's body was found in a classroom, slumped over young children killed in the shooting. The 52-year-old special education teacher was apparently attempting to shield them, her father told the newspaper Newsday.

Aspirations were cut short and potential was wiped out -- of the young children who will no longer learn and grow toward adulthood, but also of the teachers who died.

Rachel D'Avino, 29, was a behavioral therapist who worked with autistic children. D'Avino's boyfriend was going to propose to her on Christmas Eve.

Lauren Rousseau, 30, had dreamed of being a teacher since before she went to kindergarten herself. She had been hired only last month by Sandy Hook and was substituting for a teacher on maternity leave when Lanza killed her.

For the teachers who lived through the carnage, difficult tasks lie ahead.

In the coming days, they will bury their colleagues and 20 small children they taught and adored, while comforting parents and nursing the tender hearts of the children who survived.

Kindergarten teacher Janet Vollmer knows at least half of the killed children.

"Ten of them were in my class last year," she told CNN's Anderson Cooper on Sunday. "It's tough. It's tough."