Washington (CNN) Her lip trembled as she stood outside a federal courthouse in Washington Thursday. Beata Mariana de Jesus Mejia-Mejia had just gotten the news she'd been waiting a month to hear.

Authorities are planning to release her 7-year-old son, Darwin, from a shelter in Phoenix, Arizona. He could be back in her arms by late Thursday night, according to Mejia's legal team.

Beata Mariana de Jesus Mejia-Mejia sued the government, asking to be reunited with her son.

The 38-year-old Guatemalan mother says she and her and son were separated at an immigration holding facility in mid-May, just a few days after they crossed the US-Mexico border.

This week, Mejia filed a lawsuit against several government agencies and top Trump administration officials to get Darwin back. Lawyers announced in court Thursday that an agreement had been reached just minutes before a hearing in the high-profile case was to start.

Even as they celebrated what appeared to be a victory, members of Mejia's legal team said their fight wasn't over as long as immigrant parents and kids remained separated as a result of the Trump administration's policies.

"This child is not the only child," attorney Mario Williams said. "There's thousands of children similarly situated we have to do something about."

Mejia told reporters she was happy to hear the news, but still had only one thing on her mind.

"I just want to have my son," she said.

'A knife in your chest'

Mejia told CNN this week that she'd been trying to learn her son's whereabouts for weeks. But no one had given her a clear answer.

Mejia says she took this selfie of her and her son at their church in Guatemala.

"It's not fair for a mother," she said. "It's like they're putting a knife in your chest and killing you."

Meija's case isn't the only lawsuit challenging the Trump administration's months-long practice of separating kids and parents at the border, but it appears to be the first filed by an individual since officials announced their controversial "zero tolerance" policy.

On Wednesday a group of detained immigrants filed a similar lawsuit asking a federal court to reunite them with their children. And the ACLU has filed a class action lawsuit over family separations.

In an executive order Wednesday, Trump said he was reversing course and would be moving toward keeping families together in detention rather than splitting them up. But it's unclear how the executive order could affect families who were already separated. Officials with the Department of Health and Human Services (HHS) have said they're awaiting guidance.

Seeking a reunion, and damages

Mejia says she and her son came to the United States seeking asylum, fleeing death threats and domestic violence from her husband in Guatemala. They crossed the border May 19 near San Luis, Arizona, according to the lawsuit, and were immediately approached by Border Patrol agents and taken into custody.

In her lawsuit, Mejia accuses US officials of violating her rights when they took Darwin from her at an Arizona immigrant holding facility just a few days after their arrival.

She asked a judge to order officials to reunite them and said she was seeking damages for pain and suffering.

It's unclear whether the case will proceed once the mother and son are reunited.

Immigration and Customs Enforcement officials have not responded to CNN's requests for information on Mejia's immigration case. And the HHS Administration for Children and Families, which runs shelters that house unaccompanied minors and children separated from their parents, hasn't responded to a request for comment on her son's case.

The Department of Homeland Security and US Customs and Border Protection declined to comment, citing their policy of not discussing pending litigation.

Their last days together

Mejia pointed to two photos of her son earlier this week as she spoke with reporters and pleaded for help with her case: a smiling selfie she said she snapped at their church in Guatemala, and a black-and-white photo US immigration authorities took after taking them into custody.

In that photo, Mejia is carrying her son on her back. She's smiling. He's sleeping, his head resting on her shoulder.

It was just a few days later, she says, that their world turned upside down.

Mejia says she never expected officials would take Darwin from her. The day they did, she says, they offered no explanation. They simply called his name, took him away and wouldn't answer any questions, she says.

According to the lawsuit, when officials took away her son, "he was screaming and crying and did not want to be taken away from his mother."

Mejia says that was the last time she saw him.

'They don't give anyone any answers'

Mejia was held for weeks at the Eloy Detention Center in Arizona, where she says she met many other women who were also frantically searching for their children after being separated at the border.

"They don't give anyone any answers," she says, though she says she did hear one official respond with a question: "Who sent you to come to my country?"

At one point, according to the lawsuit, an officer at Eloy told Mejia her son was being held at a facility in Phoenix, but Mejia says officials provided no additional details on his whereabouts.

Mejia was released from custody June 15 after an immigration bond company, Libre by Nexus, paid her $12,500 bond. A legal division of the company is representing her in court.

The bond payment and legal representation are being provided pro bono as part of a program for indigent clients, Nexus Services CEO Mike Donovan says.

Speaking outside the federal court Thursday, Donovan said he hoped to turn Mejia's case into a class action lawsuit to help other parents reunite with their children.

"It is time to put this very dark and sad and sick and disgusting chapter of American history behind us," he said.

Libre by Nexus has faced accusations of exploiting immigrants and is reportedly under investigation in several states over its practices

Asked about the allegations earlier, Donovan says Mejia's case is just one example of how his company's actions speak louder that any words.

"I care about people. I want mass incarceration in this country to end. And I want incarceration without justification, and incarceration of little kids, especially, to end," he said.

His voice on the phone sounded different

Mejia says she's been living with a friend in Austin, Texas, since her release from custody, but traveled to Washington this week for the court hearing. She was accompanied by her lawyers and representatives of Libre by Nexus when she spoke to CNN.

Mejia says she's afraid something has happened to her son during their time apart. They were only able to speak on the phone once while she was detained, she says. That day, she says, an official helped them get in touch after she passed her credible fear screening -- a step that cleared the way for her to continue with her asylum case.

The voice on the other end of the line, she says, didn't sound like her son at all. Her normally vibrant child didn't call her Mami like he usually does, she says. In fact, he didn't say much at all.

"I didn't recognize him, because he didn't talk to me like that before, with sadness, a knot in his throat," she says.

She asked how he was. "Fine," he told her. But right away, she says she sensed that he wasn't.

"He is already different. I don't know what's happening," Mejia says. "I don't know if he's being threatened or what is happening with them, because my son was not like that."

Mejia says she tried repeatedly to call the number officials gave her to track down her son. It rang and rang, she says, but most of the time, no one answered.

On Wednesday evening, she was able to get through. She told her son the ordeal would be over soon.

She told reporters Thursday she's starting to plan for their life in the United States. She wants to buy him a soccer ball and a bicycle. And she'll keep fighting for her son.

Her goal, now that he'll soon be back by her side: to give him a good education.