20/20: In an Instant

It was just after 1 p.m. on May 20, 2013 when the Storm Prediction Center issued a tornado watch for Eastern Oklahoma. Two hours later, storm spotters confirmed that an EF5 tornado had touched down and was ripping across the state towards the city of Moore, where school was in session.

As sirens blared, teachers at Plaza Towers Elementary donned brave faces while bracing the students for impact. Talking for the first time ever on television, teacher Jennifer Doan, whose Plaza Towers class was the hardest hit, shares her very personal story of tragedy and triumph left in the tornado's wake.

Jae Lowder checked into Alta View Hospital expecting to have a baby, but soon she was caught in a violent hostage crisis. She remembers hearing her baby crying…then gunshots…then silence. It would be 18 hours before Jae would know if a gun-wielding man on a rampage had killed her son Bryan in the nursery. New mom Cindy Tovey could only listen to the scene outside her room unfold in terror since she could not move, temporarily paralyzed from the waist down after a C-section. Like Jae Lowder, she spent agonizing hours wondering if her newborn was dead or alive.

Rick Worthington, a father of eight, had burst into the hospital and vowed to start "shooting babies" if he did not find the doctor who performed a tubal ligation surgery on his wife two years earlier. Worthington erroneously claimed the doctor performed the procedure without his wife's knowledge or consent while she was sleeping.

Glade Curtis, sharing his story for the first time ever on television, was the doctor Worthington came to kill. He was at Alta View that night and called 911 after doing what he could to get babies out safely. But no one did more to keep moms and babies alive than the nurses, including Margie Wyler, who helped a mom deliver her baby during the crisis, and Karla Roth, who sacrificed her own life in a brave attempt to wrestle a gun away from Worthington. It would take hours before police, hostage negotiators and the SWAT team could apprehend Worthington, who had a bomb at the ready to blow up the hospital.

A marathoner falls in a canyon and breaks her pelvis while out on a training run with her dog, and the faithful canine searches for someone to rescue its injured owner.

Ashley Ware bravely fights against an attacker after being abducted from her home.

A woman and her two daughters become trapped in their crushed car, dangling over the edge of a ravine, when a high truck driver crashes into them on the highway, his own vehicle going over the edge and exploding.