U.S. Sen. Jeff Merkley (D-Ore.) sat in a downtown Portland park Friday and described the United States government crowding migrants into freezing cold cells—also known as "hieleras," or "iceboxes" in Spanish—where the lights are left on all night. He said adults and children aren't getting three meals a day, or basic access to medical care.

These are just some of the many details from the senator's account of visiting detention centers near the Mexican border, something he's done eight times.

"We don't treat people like that in the United States of America," Merkley said, to cries of "Yeah!" from the gathered audience.

He and immigration experts held a 40-minute public briefing session Friday in Terry Schrunk Plaza to discuss the latest updates on the status of migrants in detention camps on the U.S.-Mexico border, along with new developments in legal and legislative challenges the Trump administration's immigration policies.

"It's so important for our leaders around the country to talk to the public about what's happening," Merkley said to WW after the event. "It's our tax dollars, our government, our land. We all have a responsibility as citizens in a republic to be engaged and to raise our voices when we think that things are going off track."

The senator discussed a handful of bills that he's working on getting through Congress, including his recently introduced "Stop Cruelty to Migrant Children Act," which would prohibit most cases of separating families and mandate minimum health standards at the U.S. Border Patrol stations where migrant children are being held.

Related: U.S. Sen. Jeff Merkley Sponsors Bill to End Cruel Treatment of Children in Camps at Mexican Border

Some attendees held signs with handwritten messages that said: "Close the Camps" or "Impeachment Now."

One attendee, Brandie DiFalco, has been protesting daily in Pioneer Square against child detentions for about a month, holding a sign that reads, "Babies shouldn't be in cages."

"My protesting and marching is almost like an act of desperation," said DiFalco, a stay-at-home mom. "I don't know what else what to do. I can't stop what's happening, and I'm hoping that maybe he [Merkley] can give us some more action items."

An attorney with the Portland-based Innovation Law Lab, Jordan Cunnings, gave listeners a rundown of the nonprofit's work against the Trump administration's hard-line immigration policies that work to "effectively close the southern border and deny protection to immigrants fleeing persecution."

Just two weeks ago, Cunnings said, the lab and others filed a federal lawsuit against the Trump administration after it set a new law that prohibits asylum claims from anyone who has passed through another country on the way to the U.S., which would "essentially would cover anyone other than Mexican residents," according to the Los Angeles Times.

A federal judge has since put the new law on pause with a nationwide injunction, Cunnings said, but that "the fight continues."

Two doctors from the local branch of Physician Women for Democratic Principles, a grass-roots civil rights organization that focuses on activism and fundraising, also spoke.

Dr. Colleen McCormick and Dr. Andrea Chiavarini recounted other stories of abuses, mostly told to them by other doctors. Those secondhand stories included a child without an asthma inhaler, and children who shook with fear during clinical exams.

"We know that the wounds inflicted today will leave lifelong scars," McCormick said. "As physicians we are mandated to speak out against this abuse—you don't need to be a doctor to know that child abuse should not be a political platform."

Another attendee, Joshua Shulman, a Portland-based attorney, came because he's been impressed by Merkley's outspokenness and his visits to detention centers at the border. He was appalled by what he heard.

"How can this still be going on?" Shulman asked.

You can watch a livestream of the event on Merkley's Facebook page.