When Julie Marin came out as a transgender woman to her fellow officers in the San Jose Police Department, they suddenly treated her like it was her first day on the job.

One evening in her patrol car, a call came in on her radio from command to respond to a fight. She arrived on the scene, and quickly realized it was a sizeable fight. Marin called for back up, but no one answered. After absorbing the silence on her radio, she threw herself into the fray and tried to stop it herself. Finally, another officer arrived—but instead of helping, he stood and watched as Marin bore the brunt of the chaos, seeing whether she could handle it. As the violence escalated, he ultimately intervened.

“He waited until it got pretty ugly,” Marin told TakePart. “He wanted to see if I still had the courage and physical ability to deal with those kinds of situations. I had to prove myself on the street all over again.”

Nothing had changed about Marin, who had served 20 years with her colleagues before she came out in 2001, apart from her gender identity. Yet most of her colleagues treated her like a rookie and a stranger.

“I’d say 80 percent were vehemently against it [when I came out],” Marin said. “Some were really sad; others disclosed that they had transgender relatives. I found support from some people, but by and large I was cast out and rejected.”

Marin isn’t alone: There are roughly 3,000 known transgender people in law enforcement across six continents, with around 600 in the U.S., according to the support network Transgender Community of Police and Sheriffs (T-COPS). That number only includes people who have actively reached out to the organization—Patrick Callahan, the group’s public information officer, told TakePart that there he’s aware of others who either don’t want to be part of the community or aren’t aware of it.

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Marin started the group and a Yahoo chat room in 2002, after participating in a study on transgender law enforcement conducted by professor Tom Whetstone of the Southern Police Institute at the University of Louisville.

“When I first started looking around and reaching into what being transgender meant, I thought, ‘Oh God, I’m the only cop around who’s transgender,’” Marin recalled. “But that was certainly not the case. I found a lot of wisdom and solace in listening to the people that had transitioned before me.”

From there, the group grew exponentially by word of mouth, and morphed into a service- and education-based organization that connects officers to the resources they need, and provides police departments with sample polices and procedures to help them navigate the legal landscape that can come with aiding an officer as they transition on the job. Many of Marin’s own growing pains have helped the group offer insight to others.

“Bathrooms and locker rooms are consistently the largest sticking point for rank and file officers,” Callahan told TakePart. “’I don’t want that freak in my bathroom,’ they’ll say.”

Callahan, a former U.S. Marine military police officer who transitioned after leaving the service, went on to study criminology at the University of Pennsylvania, where he came across Marin’s chat group in 2005.

The success of a department’s ability to evolve with its employees usually comes from the high-ranking officers. “If command staff are supportive, usually that filters down through the ranks pretty quickly,” Callahan said.

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San Franciso, Austin, Dallas-Fort Worth, and San Diego were all mentioned by Callahan as having police or sheriff departments that have successfully and supportively navigated the process. In 2014, officer Gary Abbink became the first openly transgender cop on the Austin Police Department’s force. Earlier this year, Abbink told The Austin Chronicle that his fellow officers had been encouraging and supportive. Austin Police Chief Art Acevedo is credited by some in the community for creating a more tolerant culture in the department.

Still, plenty of transgender officers encounter the frightening challenges and alienation Marin had to endure.

“Many times individuals come to us at the end of their rope, sometimes when they’re thinking about suicide,” Callahan said. “It’s often in their late 30s, early 40s, when they have careers and families but have reached a point in their life where they can no longer maintain the façade of an inappropriate gender identity.”