A group of people from very different walks of life, including a former CIA agent, two CrossFit instructors, a door-to-door salesman, and an actress who starred in The Walking Dead, teamed up with Colombian authorities to help bust an underage sex trafficking ring, reported ABC News.

Members of Operation Underground Railroad posed as attendees of a bachelor party and arranged to buy underage prostitutes, some as young as 13. While prostitution is legal in Colombia, underage prostitution is not, and those who traffic child sex workers face up to 16 years in prison.

Tim Ballard, founder of the group, told ABC’s Nightline, “I spent 12 years as a special agent, undercover operative for the United States government, doing this, and learned how to do it. The problem was that the vast majority of the kids that we would identify, we couldn’t save. They weren’t US cases.”

Operation Underground Railroad worked for months to put together the elaborate sting operation with the Colombian authorities. They rented a huge house in Cartagena, put up surveillance cameras, and even decorated the outside of the house so that it would seem normal for teenage girls to be dropped off.

Colombian officials hid, waiting for the girls and their traffickers to arrive. They had to wait for Ballard and his team to get the traffickers to explicitly say the girls were there to provide sexual favors for the bachelor party and the money to change hands.

Once it did, the authorities rushed in, arresting the traffickers and pretending to arrest Ballard and the members of his group to keep up appearances. The trafficker, of course, denied any wrongdoing and claimed that all the girls were of age, and he had lied to Ballard and his friends to make them “happy.”

Social workers were on hand to assist the girls, 17 of whom were underage, either with fake IDs or no identification at all.

The entire operation was filmed for an upcoming documentary, The Abolitionists, by filmmakers Chet Thomas and Darrin Fletcher. Nightline also filmed the sting.

Watch Nightline’s coverage of the incident.