AMHERST — It was Monday night when Lucio Perez doubled over in pain. A quick visit by his doctor confirmed that his appendix was inflamed and on the verge of bursting. For most people, this would mean an immediate trip to the hospital for routine surgery.

But Perez is in the country illegally and has spent the past seven months sheltered at a church in Amherst, wearing a GPS device on his ankle that alerts immigration officials to his every move. Perez’s supporters feared that taking him to the hospital would put him at risk of being arrested and deported.

But this was a medical emergency. Perez had to leave the church.

So on Monday night, he left the church for the first time since October and rode in the back of an ambulance to Cooley Dickinson Hospital in Northampton.

His ankle bracelet was beeping because its battery was low, he said. His phone started ringing and he could see that it was Immigrations and Customs Enforcement, he said. He did not answer it.

Perez’s appendix was removed at the hospital and he was ready to leave by Thursday.

But his supporters worried that federal immigration agents — newly emboldened by President Trump’s hard-line stance against illegal immigration — would try to apprehend Perez outside the hospital or during the 10-mile car ride back to the church. So they devised a plan to try to protect him.

As he left the hospital Thursday, about 40 supporters, including Northampton Mayor David Narkewicz, stood on either side of a walkway outside Cooley Dickinson, holding flowers.

Perez ducked quickly into the back of a waiting Subaru with Narkewicz in the front seat, and rode toward the church, as the activists ran to their cars and formed a caravan to escort him along the route. Fifteen minutes later, Perez was back inside the sanctuary, as his supporters exhaled.

“Thank goodness he’s not in an ICE van,’’ said Margaret Sawyer, a pastor and lead organizer at the Pioneer Valley Workers Center, one of the groups helping Perez.

After spending a few minutes inside the church, Perez emerged with his wife, Dora, a bandage visible on his wrist from an IV.

Sitting in a chair, he greeted supporters who hugged him, kissed him, and handed him flowers.

“Well, obviously, these past few days have been very sad for me,’’ Perez, a 38-year-old father of four from Guatemala who came to the US in 1999, said through a Spanish translator. “But in this moment, I feel so happy to have so many around me. This will be a day that will forever mark my life.’’

Cooley Dickinson Hospital defended its role in the drama, saying in a statement that it “welcomes and treats all patients without regard to immigration status’’ and will not provide immigration authorities information about its patients “unless compelled by law.’’

“It is our job is to improve health, save lives, and create a healthy community regardless of what our patients or colleagues look like, what they believe, who they love, where they come from, and how they got here,’’ the hospital said.

John Mohan, a spokesman for Immigration and Customs Enforcement, dismissed the notion that agents would have sought to arrest Perez outside the hospital or en route to the church.

“There was no attempt, nor would there have been an attempt to apprehend this individual in the manner suggested by some of those involved in these events,’’ he said in a statement. “Current ICE policy directs agency personnel to avoid conducting enforcement activities at sensitive locations unless they have prior approval from an appropriate supervisory official or in the event of exigent circumstances. The locations specified in the guidance include schools, places of worship, and hospitals.’’

Perez, a landscaper who had been living with his family in Springfield, has said he first came to the attention of immigration authorities in 2009, when he stopped for a coffee at a Connecticut gas station and was arrested for child abandonment because he had left his young children in the car while he went into the store. He said the charges were later dropped.

He said that, during the Obama administration, he was granted stays of removal every year. In August, however, under the Trump administration, he was told to buy a ticket to Guatemala for Oct. 19 after his stay was denied, said Rose Bookbinder, an organizer with Massachusetts Jobs for Justice.

Instead of leaving the country, Perez took refuge in Amherst’s First Congregational Church, one of several churches across the state that is providing sanctuary to immigrants facing deportation.

Addressing Perez’s supporters outside the church on Thursday, the Rev. Vicki Kemper, pastor of First Congregational, said sheltering Perez was an expression of religious conviction because “our faith calls us to welcome the stranger.’’

Still, she said, “this is not where we want him to be.’’

“We want him to be home,’’ Kemper said, “his own home, with his own wife and children.’’

Supporters from the Pioneer Valley Workers Center, Jobs with Justice, and other groups from Western Massachusetts have been bringing Perez food and shuttling his wife and children to the church to visit him.

But he said being separated from his family has been “terrible.’’

“That’s why many people have expressed to me their love and have never abandoned for me a single second,’’ he said, adding that even during his four days in the hospital, he was never alone.

But Perez said his medical ordeal was hard on his children, who are already afraid to go to school because they worry he could be arrested and sent back to Guatemala.

He said he hopes some day he can leave the church and reunite with his family at home.

“Although I’m going to be here for an uncertain amount of time, I will continue to live here in this church, hoping that this problem will resolve itself,’’ he said.

NORTHAMPTON — Lucio Perez’s potentially fraught journey began at the Cooley Dickinson Hospital, where clergy members prayed for his safe delivery.

About 40 supporters, including Northampton Mayor David Narkewicz, formed a corridor as Perez left the hospital with an escort.

AMHERST — Perez (center) thanked Milta Franco, of Springfield, and other supporters after arriving back at the First Congregational Church, where he has sought sanctuary since October. He had needed an emergency appendectomy.

Michael Levenson can be reached at michael.levenson@globe.com