McALLEN, Texas – The old-fashioned trolley bus stopped just outside Sacred Heart Catholic Church, and eight or so passengers – new immigrants who had just stolen across the Rio Grande from Mexico – filed off, clutching water bottles and manila envelopes marked with their intended destinations in the U.S.

A man, frowning, headed for the door of the church with a young girl in tow. So did several women clutching children, looking dazed when a large group of volunteers suddenly stopped what they were doing and raised their hands in applause. “Bienvenidos,” said one. Welcome. The new arrivals were ushered inside.

“This is the first experience a lot of people here have of meeting an American,” explained Cesar Riojas, 50, one of hundreds of south Texas residents who have transformed the squat brick church hall here into a bustling support center for the hundreds of new immigrants now crossing into the U.S. from Mexico each week.

“I put myself in their position,” Riojas said. “How would I want to be treated?”

The surge of about 57,000 unaccompanied youths since October and large numbers of immigrating parents with children has thrown the Obama administration’s immigration policy into disarray and sparked new demands across the U.S. for heightened border security. But in the Rio Grande Valley, a porous frontier traveled by illicit wayfarers throughout history, the new influx of children and parents from Central America has been most immediately a reason to get to work.

The estimated 800 volunteers at the hastily organized immigrant relief center are retirees and businessmen, stay-at-home moms and students from nearby University of Texas-Pan American. Organizers from Catholic Charities have been joined by the Salvation Army, by Baptists, Methodists and Episcopalians. Teachers have brought their classes. An evangelical radio host summoned followers. In a region where many residents live in shacks and trailers without electricity, the center has received so much donated food that much of it is being stored offsite.

“The more you have, the more you separate yourself from those who have nothing,” said Riojas, a self-described conservative Republican from nearby Harlingen who is taking time off from his job as a consultant.

Valley residents started the relief center about a month ago with the help of a local nun after meeting immigrant families by chance at the bus station. They began organizing on Facebook and persuaded the church to let them use the hall.

Since then, the facility has served more than 3,000 immigrants, at times 200 a day. There are a few paid staffers, and volunteers work in shifts with assigned duties. Small teams lead immigrants through the process of getting bathed, clothed and bused to destinations around the U.S. where they will remain with friends or family until their immigration cases are heard in court. With many too traumatized and exhausted to hold down food, the newest are offered chicken soup and bottles of Pedialyte.

Massive tents in the parking lot have been set up as sleeping quarters for up to 60 adults awaiting buses, with portable showers and toilets nearby, donated by Hidalgo County. A local Baptist church brought a portable laundry.

“The community here have been very welcoming,” said Sarita Fritzler, the Washington-based team leader for the charity Save the Children, who recently arrived from running a similar effort for Syrian refugees in Iraq.

Jose Luis Zelaya, 27, a doctoral student at Texas A&M University, about 380 miles north, who is studying to become a teacher, also volunteers. He was an immigrant himself under similar circumstances when he arrived in the valley 14 years ago as an unaccompanied minor from the gang-plagued Honduran city of San Pedro Sula.

Zelaya said he was familiar with the tales of violence and trauma many of the new immigrants tell – before leaving his home to join his mother and his 9-year-old sister in Texas, he said, he’d been threatened by a gang, shot in each arm while he was playing soccer.

Just 13 years old at the time, Zelaya memorized his mother’s phone number in Texas and boarded the train through Mexico that has ferried thousands of Central American immigrants on similar journeys over the years. He saw children raped, he said, and a man who fell from atop the hurtling train to his death. When he made it to the Rio Grande, he swam across alone and fell asleep in some bushes, where the Border Patrol found him.

Zelaya went on to graduate from high school and Texas A&M, and is now staying in the country under President Obama’s Deferred Action for Childhood Arrivals program.

“I understand what they’re going through,” he said of his decision to come help the newest arrivals. “I understand the journey, what it is to be in a detention center and what they can have if they’re reunited” with families, he said. “I know our country is grappling with this. If we send them back, they’re being sent back to death.”

Ofelia De Los Santos, a native of nearby Edinburg who is coordinating volunteers, said she can’t help but think of her 18-year-old grandson.

“He’s never had to run for his life, to be thirsty or hungry,” she said, her voice catching as she removed her glasses. “You go home and think: What would I do if my children were being recruited by those gangs? Would I sell my house and send my children north?”

In the early days of the relief effort, volunteers were walking families from the bus station at all hours, mothers leading children by the hand through a series of back alleys where drifters lurked and broken glass glittered underfoot. Those with longer layovers they took into their homes, providing food and a place to rest.

Now the process is more formal. Arrivals are announced by loudspeaker and ushered through.

“Who’s my volunteer with this family?” called out Hermi Forshage, handling intake last week at a table marked “Catholic Charities Disaster Response.”

Forshage, 54, was working with a Guatemalan mother and her teenage son, reviewing their immigration paperwork and bus itinerary to Mobile, Ala.

“They’re very, very scared,” she told the volunteers before handing them off. “They don’t speak Spanish. She knows ‘si’ very well, though, right?” Forshage said.

The woman, who spoke an indigenous language, nodded. “Si.”

They shared a fragile smile. The woman looked relieved.

“She likes to cry,” Forshage said. “She’s already made me cry once.”

A volunteer named Sandy in a red San Antonio Spurs cap moved the pair to pick new outfits from the dozens of folding tables stacked with clothes, toiletries and other supplies, sorted by age, sex and size.

A new pair took their place in front of Forshage – this time a Salvadoran father and his small daughter, clutching a stuffed purple hedgehog labeled “Kiss me.”

Forshage brightened. “How old are you?” she asked.

The girl held up three fingers.

“This is hard,” Forshage sighed, reviewing the pair’s bus tickets to Indiana and handing them a sign that read, “Please help me, I do not speak English, what bus do I need to take?”

Some of the new arrivals have been pregnant women; a few were women who gave birth after crossing and showed up with babies in their arms.

Carmen Garza, 46, a mother of four from nearby Mission, said some skeptical friends had asked why the immigrants kept coming, and whether they carried diseases. She said she tried not to judge the immigrants. She grew up just over the border in Mexico, where she has relatives and her husband still works.

“Who are we to judge them? We’ve led a privileged life,” she said.