(CNN) Pastor Angel Campos received a voicemail that terrified him. Someone said his children should be raped.

The call had come in only after posts appeared on social media documenting his efforts to help refugees and immigrants released from custody, along with other churches in Arizona who work with ICE to assist asylum seekers.

Nobody can say who made the call. But it is part of a tactic, according to the Southern Poverty Law Center, used by groups to frighten activists. Several anti-immigration groups in Arizona have recently filmed videos and posted them on Facebook encouraging people to contact pastors and churches helping asylum seekers.

And then the in-person confrontations started, between sometimes virulent anti-immigration groups and churches trying to help those seeking asylum. Now that battle is going to play out in federal court.

Pastors and churches in and around the Phoenix area are suing the Patriot Movement AZ and AZ Patriots groups, as well as several individuals, alleging they are "illegally intimidating, threatening, harassing" and trespassing on church property when they come to scream at immigrants being dropped off at the churches. The lawsuit was filed Tuesday in the US District Court for the District of Arizona with the help of lawyers from the Southern Poverty Law Center.

"The harassment we have endured is illegal, terrifying, and absolutely not acceptable," Campos told CNN. "The defendants have made the children, volunteers, and staff feel fearful, threatened, and intimidated."

The lawsuit offers a window into the methods and messaging of some of the most organized opponents of immigration near the US border with Mexico.

The suit names two Arizona-based groups, who were once one group but have since splintered. The pastors and churches also specifically named the founder of Patriot Movement AZ, Lesa Antone, and another leader of the group, Russell "RJ" Jaffe. Antonio Foreman, who according to the lawsuit has visited at least one church with the group, is alleged to be affiliated with multiple white nationalist hate groups and attended the "Unite the Right" rally in Charlottesville. The suit also names Jennifer Harrison and Jeremy Bronaugh, who were members of Patriot Movement AZ before splitting off and creating their own group, AZ Patriots.

Pastor Campos says he has been filmed and accused of being paid to assist immigrants, and that Harrison and Antone have accused his church of "breaking the law" as well as "aiding and abetting," according to the lawsuit. Antone argued with a volunteer at Campos' church when "someone among the Defendants chanted 'punch her,'" according to the lawsuit.

"The invasive videos and false statements the defendants have posted online have accused us of crimes and have also dehumanized the people we are trying to help," Campos said. "We are in constant fear for our safety and the safety of our families and the community members who support our work.

"We do this work because we believe that there is a higher power helping us all. Just like other churches, we want to continue helping every member of the Phoenix community, including the most vulnerable among us."

CNN has reached out to, but not heard back from, all those named in the lawsuit. Jennifer Harrison told CNN she had not seen the lawsuit, but says she believes her actions are "protected under the first amendment."

"We opposed illegal immigration. We oppose people entering the country illegally and we oppose the churches that aid and abet and give a free ride and reward people for entering this country illegally under the false pretense of asylum," she told CNN. "No laws were broken. There are no police reports as far as being trespassed or entering after trespass. We are well within our rights. Just because they don't like what we're saying doesn't make it harassment."

Lesa Antone told CNN she had "broken no laws" but also had not seen the lawsuit and could not comment further besides saying, "It is a frivolous lawsuit by an illegitimate group that targets conservatives and conservative Americans and that I welcome it."

Filming the encounters

The groups often post videos online of themselves following DHS and ICE buses to the churches before getting out and filming.

In one video, according to the lawsuit, as people get off a DHS bus, Harrison says to someone nearby, "Hopefully, ma'am, they don't get loose and rape any of those little kids." Some members of the groups have also taken trips to the border where they shout derogatory comments at immigrants, according to videos posted on Facebook.

The lawsuit includes seven different counts, including conspiracy to violate civil rights, defamation and trespassing.

It claims that the groups "are motivated, at least in part, by animus against Central Americans and people of color" and "through their illegal actions, they are attempting to prevent Plaintiffs from assisting Immigrants from Central America and Immigrants who are people of color."

Both Patriot groups have openly filmed themselves and shared videos on social media sites showing themselves screaming at immigrants, telling them to go back to Mexico and then making allegations against the pastors and volunteers at the churches.

In the lawsuit the pastors and churches are asking for an injunction against what they call the illegal actions and damages. They make clear they are not asking the court to stop the groups from "expressing their opinions" but to do so within a safe distance of the churches, and that the defendants stop "intimidating, threatening, harassing or otherwise interfering" with the churches' efforts to aid the migrants.

The churches began helping migrants toward the end of 2018, and shortly after they advertised the need for volunteers, the patriot groups began showing up, according to the lawsuit.

The encounters, which are often livestreamed on Facebook or on the groups' YouTube pages, usually unfold the same way regardless of what church the group visits.

The lawsuit states that Foreman wrote on his Facebook page that he once forced his way into a church in January 2019 while it was receiving immigrants and declared he was homeless and demanded to be fed. He was armed at the time, according to the lawsuit. And a video posted online shows him bragging about the encounter with a gun holstered on his hip.

In another case, in January 2019, Jennifer Harrison went to a church in Mesa after an ICE bus arrived and began shouting "fuera" (get out, in Spanish) at the people getting off the bus, according to a video posted on the group's Facebook page and the lawsuit.

Harrison singled out Magdalena Schwartz, a pastor and coordinator, who was at the church that day, according to the lawsuit.

"Magdalena, you know what you're doing. You know those kids don't belong to those men," Harrison shouted at her while filming, according to a video posted on Facebook and detailed in the lawsuit. "How much are you getting paid, Magdalena? How much are you being paid to human traffic children?"

The human trafficking allegation is often repeated in a variety of videos by both groups. The videos have thousands of views on Facebook.

On another occasion in January 2019, Harrison, Antone, Foreman and others yelled at Pastor Elias Garcia at another church, according to the lawsuit.

"These churches are complicit in human and child trafficking," they yelled according to the lawsuit. "This is the United States of America and you are breaking our laws, criminals."

David Dinielli, deputy legal director at the SPLC, say groups like Patriot Movement AZ and AZ Patriots have given voice to "fear and bigotry" and that "their harassment is lawless."

"Their threats have prevented our clients from helping people in need," he said. "They're motivated by the simple fact that the people our clients have chosen to help look and sound, to these purported 'patriots,' as if they don't belong."

Schwartz and the other pastors reject that they have done anything wrong and are frustrated by the characterization of the work they are doing.

"Our churches, pastors, and volunteers make many sacrifices to help these families, but the defendants force us to do so in fear," Schwartz said in an SPLC press release. "We are not breaking the law, but the defendants threaten us and accuse us of being law-breakers. We have been repeatedly targeted by the defendants, and now we will ask the court to stop this behavior so that we can continue our mission in peace."