Jeremy Hammer was at a crowded college party in Virginia last month when he heard a loud bang. There were gasps, followed by a scream. Then everyone began rushing toward the exits.

Hammer remembers feeling terrified. “It was one of those moments where you’re like, ‘Oh my God, it’s my turn.’” It took a minute to grasp that the noise was not a gunshot, but a burst balloon.

Jen Panos is a mother of three in California. She finds herself noting what her kids are wearing to school. If there is a shooting, she thinks, she needs to be able to identify their bodies. “I walk myself through it: What am I going to do if this comes for us?” she said.

Kat Vargas and her husband, a firefighter, live in Texas. They too have a plan for what to do in the event of a shooting: Vargas would cover their youngest, while […]