On Valentine’s Day 2018, Bruna Oliveira’s geography teacher was shot dead at her feet as he ushered students into his classroom to shield them from an approaching gunman. Crouched near his body, holding her breath, the girl feared she would be killed next — dead at 14. But the shooter moved down the hallway on his rampage.

When the massacre at Marjory Stoneman Douglas High School in Parkland, Fla., occurred, Ms. Oliveira’s Brazilian family was living temporarily in the United States with no intention of staying. Her mother, an architect enrolled in an English immersion program, had brought her two children along on her student visa.

But the worst high school shooting in U.S. history made Ms. Oliveira an American, or a would-be American. It was a baptism by bullet, not just for her but also for scores of other immigrant and international students at her school. Many had fled their homelands to escape violence, and now their journey was turned on its head. While their horrified relatives urged them to return to their native countries, the teens, bonded by trauma, dug in their heels.

“It was a massive event that took a real toll on us, but it also, like, truly bonded us forever — to each other and to this country,” said Ms. Oliveira, now a pre-med college senior who aspires to be an emergency medicine doctor because of her experience.

Advised that the government offers a special visa to victims of serious crime who are helpful to law enforcement, Ms. Oliveira and 74 other survivors of the massacre applied for what is known as a U visa.

Little did they know then that the well-intentioned U visa program is among the most dysfunctional in the whole troubled immigration apparatus, with benefits far more delayed than those of the notoriously backlogged asylum program.

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