The first Friday in May started with a sprint up a gravel road on a lush hillside outside San Juan, Puerto Rico, and it ended with the crackle of gunfire. For Tai, a 32-year-old FBI special agent who normally investigates public corruption cases on the U.S. island territory, there was nowhere else she’d rather be.

It was day one of New Operator Training School, or NOTS, a 10-week proving ground for selectees to the San Juan Division’s SWAT team, which is among the busiest of the FBI’s 56 field office teams. Tai and four other special agents would spend the day—and the next nine Fridays—practicing, refining, and repeating how to safely enter rooms and effectively handle SWAT firearms. Each of the agents had something to prove— that they belonged there. For Tai, who is believed to be the first African American woman in the Bureau’s history to be selected for an FBI SWAT team, the weight of the milestone wasn’t on her mind; on this humid May morning, she was singularly focused on clearing rooms, hitting targets, and moving and thinking in fluid synchronicity with her teammates.

“I’m one of those people where I have a task at hand and I just focus on that task,” said Tai, whose last name we are withholding. “I don’t really think about people looking at me.”

Tai, who is also a soldier in the U.S. Army Reserve, joined the FBI four years ago and has spent her career in Puerto Rico working corruption cases involving nonelected officials. Before the FBI, she was a deputy for five years in the Orange County Sheriff’s Office in Orlando, Florida. She was drawn to the FBI after seeing the Bureau’s response to a mass shooting in 2016 at the Pulse nightclub in Orlando, where 49 people were killed. “The amount of assets and the professional attitude of agents,” she said. “They were organized, and they got stuff done.”

One of Tai’s fellow Army Reserve officers suggested that she would be a good FBI agent. She applied, went through new agent training, and was assigned to the San Juan Field Office in 2017. Almost four years later, Tai and four other agents were sweating under the heat of a tropical sun, tactical vests, and the exacting scrutiny of field-hardened instructors training up a new cadre of SWAT operators.

“We want everyone to get through NOTS,” said Special Agent Owen Reese, a SWAT operator leading the training course. “But we’re also prepared to tell someone, ‘Hey, you’re not getting it. Maybe this isn’t the right job for you.’ Because it’s not for every body.”

The 10-week NOTS course prepares SWAT selectees for operations (SWAT stands for special weapons and tactics). The training crucible makes them more proficient at firearms, body movement, and critical thinking in stressful situations. If they pass, Reese said, they join their field office’s SWAT team as probationary members—meaning they can do everything except enter houses. Probation may last six to 18 months as the new operators gain experience. They are then sent to SWAT Basic at the FBI Training Academy in Virginia, where new operators from all the FBI’s field offices go through three weeks of training to get officially certified by the body that oversees FBI SWAT operations, the Critical Incident Response Group.

“The training is standardized to make sure everyone’s on the same baseline—that we’re all doing the same thing,” Reese said. “They want someone to be up to speed for Basic and be able to pass Basic. But for our team, we’re not focusing on just passing Basic. We want them to go and crush Basic.”

Tai isn’t thinking about SWAT certification yet. It’s a long way off. And it’s early days at NOTS, so nothing is certain. When asked about breaking through barriers— figuratively—as the first Black female agent selected for SWAT, she acknowledged that her path thus far might inspire others.