"Sex tourism is a huge draw for a lot of people from North America and Europeans," Mackle explained. "Costa Rica is called the 'Thailand of the West.'"
He particularly remembers a 5-year-old girl named Grace and her 6-year-old sister who were living in a safe house in Managua after being rescued from a brothel where they'd been sold by their grandmother. The owner of the safe house returned them to their mother, who'd been working as a prostitute, because she seemed to have turned her life around.
"But she was still working on the streets as a prostitute and had a drug addiction," Mackle said. "Once again the grandmother took the granddaughters and sold them again into the brothel.
"The guy running the safe house went out to raid the brothel and on his way over, the police heard about it and tipped off the head pimps of the brothel to move the girls."
Eventually the safe house owner found and rescued the little girls again and they are beginning to recover from their exploitation.
"I can't wrap my head around the atrocities that happened to them. Their innocence has been stolen from them," Mackle said. "But to see these girls playing and to be in a loving environment, it was really incredible."
Such safe houses are just a Band-Aid, Mackle noted. His team of five young adults is trying to get to the root of the problem with its documentary, "Of Broken Wings." They are recording a story in each country in Central America to make people aware that right in their own back yards children are being sold into prostitution.
Mackle graduated from Amador Valley High in 2010 and moved to Costa Rica, where he lived for five months working with an organization called Youth with a Mission.
"Afterward I trekked deep into the Honduran jungle where I lived with the Miskito tribe for six months, helping lead and run a school," he recalled. "It was a completely different experience from anything I'd ever done. There was no electricity or running water. At nighttime I took showers from the well -- I'd pour water over my head.
"It was the hottest I've ever been, for sure, and it was humid all day long," he continued.
His diet was beans, rice and occasionally mangoes, bananas or other tropical fruits.
"I really loved being completely immersed in something I'd had no idea about," Mackle said, "being among the poorest people in the western hemisphere -- to learn their culture -- and building relationships with people when I didn't even speak the same language."
In Costa Rica he met another young person working at a mission, a Guatemalan who was also a photographer. He shared his vision with Mackle about helping exploited sex workers by forming a team to document the stories.
"We had met and worked with many prostitutes, trying to help them find a better life and get off the streets," Mackle said. "It soon came to our attention that a large majority of these prostitutes were minors, and many had been trafficked from other countries or rural towns within the country."
The team began filming in November, and spent 25 days in Honduras and Nicaragua.
"We have now heard the stories of these women and children, and we cannot walk away without doing everything we can to make a difference," Mackle said.
He returned to Pleasanton for the holidays and appeared on NBC's morning news show, Today in the Bay Area, on Jan. 14 to tell his story and ask for funding. Then he headed back to Central America to travel from Panama to Belize to interview victims.
Once the documentary is completed they plan to show it at universities.
"Our main focus is toward the young educated group in Central America," Mackle said. "They're going to be turning into lawyers and people in government. We want to be able to tell them that they can do something."
"People we tell about it in universities are completely blown away," he added. "They can't believe it is happening, that even two blocks away there are brothels with children."
The team has a goal of $15,000 to finance the documentary; donations can be made at iamactive.org/ofbrokenwings. By Wednesday, they'd received $9,395, or 63% of their goal.
Although he has collected many heartbreaking stories from the victims of human trafficking, Mackle likes to think about little Grace and her sister playing happily in the yard of the safe house in Managua.
"To see that you can save someone from a brothel and they can live their childhood free from those things -- that was the beauty of the whole thing," he said.