Joshua Rubin, a lifelong New Yorker, was outraged about children being separated from their parents at the Mexican border. The final straw was the massive tent city of detained migrant teenagers in a tiny Texas town straddling the desert and the Rio Grande.

So he climbed into his camper, kissed his wife and adult son, and made the 2,200-mile drive from New York to Tornillo.

“I was sure there’d be lots of people protesting,” said Rubin, a 67-year-old software engineer who lives in Brooklyn.

Once he arrived in mid-October, however, Rubin found there weren’t as many people protesting as he’d hoped. In fact, on many days, he’s the only one.

It’s been more than two months, and Rubin has become a fixture outside the vast detention site, a one-man vigil holding signs that read “Free them” and “Estamos de tu lado” (“We’re on your side”). He wants to show the migrant children that they are not forgotten, that people like him care.

His often solitary vigil in the desert is a measure of one man’s commitment to a cause.

Rubin documents what he sees, and from his command center in his camper he posts to social media and attempts to bring other protesters to Tornillo. He also tries to be a friendly face — albeit from afar — for the teens.

“I wave as they go in, and I wave as they go out,” Rubin said.

When he sees them enter for the first time, he said, he finds it emotional because they have no idea what lies ahead.

“It’s hard on the heart,” he said.

The Tornillo migrant detention camp houses teens between ages 13 and 17, most of whom crossed the border unaccompanied and are waiting to be reunited with parents, relatives or other sponsors as their immigration cases are processed. The amount of time it takes to vet potential sponsors for unaccompanied minors continues to grow. As of November, the average time a child spends in federal custody is 90 days, but many have been in Tornillo much longer. The Trump administration recently eased screening of potential sponsors, a change aimed at speeding the release of minors.

When Rubin started his protest, there were about 1,000 teens there. Last week the estimate was closer to 3,000.

At Tornillo, Rubin has been documenting the transformation of the tent city into a semi-permanent site with its own soccer field and commissary.

“Tents have been added. Hard shelters have been added. They bring in generators constantly,” he said.

The detention camp in Tornillo has been under increasing criticism after a report that the camp’s more than 2,000 employees had not been given FBI background checks, a violation of the guidelines of the Department of Health and Human Services.

Some of what Rubin posts to his Facebook page Witness: Tornillo are his interactions with children inside the camp.

“When I’ve actually exchanged a few words with the kids, they indicated that they weren’t particularly happy, and they also indicated that they’d spent a lot of time there,” Rubin said. “I asked how long they’ve stayed, and a few kids called out: three months … four months … five months. Some have been there since the camp was first set up back in June.”

Talking to the kids has become more difficult since about two weeks into his protest, when the chain-link and barbed-wire fence that surrounds the site was covered over with tarps of black plastic to prevent him and others from looking in.

The teens inside the Tornillo detention camp are heavily supervised by camp workers and guards. The children walk single file throughout the camp and aren’t allowed to go anywhere independently. Outside of soccer, the only form of physical contact allowed between the children is a fist bump; they aren’t allowed to hug each other.

The Tornillo detention site is one of the largest of all the facilities housing migrants and was established by the Trump administration in June to deal with an overflow of migrant detainees. That decision came during the peak of the president’s “zero tolerance” immigration crackdown, which separated around 2,500 migrant children from their parents and caused a national uproar.

Trump changed course and halted family separations on June 20, but the number of migrants crossing the border has risen in recent months. There are about 14,600 children in the custody of HHS, the highest number in the agency’s history.

Rubin has a front-row seat to this from his RV, which is parked in the unused Tornillo-Guadalupe Toll Plaza in front of the gate into the tent city. It lies in El Paso County, so the authorities at Tornillo Port of Entry cannot ask Rubin to leave.

Rubin says that camping in front of a detention center for two months is a new level of activism for him. The son of two teachers, Rubin came of age during the height of the Vietnam War in the late 1960s, witnessing friends either fleeing or resisting the draft.

Though he was never drafted, Rubin joined some of his high school friends in antiwar demonstrations and has remained politically active since. Over the summer, he made several trips to the border and demonstrated in Brownsville and McAllen, Tex., where he was arrested along with another protester for blocking the entrance to a detention center. Spending time in jail was a first for him.

It was only after attending a conference in El Paso called Grito de las Frontera (Cry From the Border) that Rubin began to think about a longer stay at one of these detention centers.

“At the conference, somebody said that she was tired of people coming down for a day and thinking that they did something,” Rubin said. “I started trying to imagine what it would be like if I came down for more than a day and what I would do.”

That’s when Rubin created Witness: Tornillo and, with the blessing of his wife and son, prepared for a longer stay.

He has emotional support from his wife, Melissa, and son, Greg, though he didn’t come home for Thanksgiving or for his wife’s birthday, and he plans to stay in Tornillo through the holidays and his son’s 30th birthday.

He says he’s making progress. People have been reaching out to him, and some have even come down to stay a night or two in their own vehicles, something Rubin says wasn’t happening when he arrived.

In mid-November, Rubin got a temporary boost when about 70 protesters came from across the country, many of them Jewish congregants led by their rabbis. This month, actress and activist Alyssa Milano interviewed Rubin while she was visiting the detention site.

Since October, the Witness: Tornillo Facebook page has gone from 67 members to more than 3,000.

“It’s also becoming an effective organizing tool,” said Rubin, who used the page to assemble a quick rally on Dec. 15 at the same time a Democratic congressional delegation that included Rep. Beto O’Rourke (D-Tex.) was visiting the detention site.

“It’s no accident that this is in Tornillo,” O’Rourke said to reporters after he toured the site. “It’s in a remote location on purpose so the American people don’t know what’s happening here.”

O’Rourke returned to the site Sunday and talked with a group of protesters who were singing Christmas carols for the detainees. O’Rourke said he’s heard progress is being made toward shutting down the detention center. He thanked “Josh” and the others who have spent time protesting at the site.

Rubin used social media to help bring volunteers to the Christmas in Tornillo event, which started Sunday and is scheduled to last until New Year’s Day. Volunteers are making an art installation of thousands of colorful paper flowers — one for each minor detained inside — that will be placed in front of the camp.

The flowers are being created and mailed by people all around the country, from churches to Girl Scout troops.

Rubin said social media will be the key to continuing the demonstrations long after his stay there is over. I can’t do this forever,” he said.

There is an online Tornillo Witnessing Sign-up sheet for people to volunteer three to four days in front of the tent city and record what they see. Rubin said volunteers are starting to line up.

“Three months is basically what I signed up for,” he said, adding he plans to leave Jan. 6. “And because of [the other volunteers], it looks like I’m going to be able to leave by then.”

Jeff Dingler is a senior writer for Saratoga Living, a magazine based in Upstate New York. He’s also a professional musician.