FREDERIC J. BROWN/AFP via Getty Images

Katie Holt's decision to have a gunshot wound kit in her classroom wasn't just a sobering reminder of America's mass shooting reality. On Thursday, it likely saved a life.

Holt, a choir teacher Saugus High School in Santa Clarita, California, used that kit to wrap the wounds of a student who ran into her room after she'd been shot. The student survived — but in this case, that single kit was barely enough, NBC News reports.

Two students were killed and three more were hurt when a 16-year-old fellow student opened fire over a 16-second period as school began Thursday morning. Those injured included the freshman girl Holt treated, who was among 30 to 40 who rushed into Holt's room. "The rookie teacher, who started in January, quickly wheeled a grand piano in front of the door and ushered dozens of her students into an office, locking the door behind them," The New York Times writes.

But after confirming the girl had been shot twice, Holt left the office and got her gunshot wound kit — she "only had one," she said. Holt wrapped the girl's wounds on her shoulder and torso while a "really brave freshman" helped apply pressure, she tells NBC News. And all around her, students were muffling their crying while one called the police and another "grabbed a fire extinguisher — just in case the gunman made it inside," the Times continued.

The alleged shooter was found after more than an hourlong search in the surrounding neighborhood and as schools in the district were locked down. The suspect was taken to a hospital for treatment of presumably self-inflicted gunshot wounds in the head and is still alive.