Updated Saturday at 2 a.m. ET

In the early hours of Wednesday, after a night spent protesting at the Multnomah County Justice Center and Mark O. Hatfield Federal Courthouse, Mark Pettibone and his friend Conner O'Shea decided to head home.

It had been a calm night compared with most protesting downtown. By 2 a.m. law enforcement hadn't used any tear gas and, with only a few exceptions, both the Portland, Ore., Police Bureau and federal law enforcement officers had stayed out of sight.

A block west of Chapman Square, Pettibone and O'Shea bumped into a group warning them that people in camouflage were driving around the area in unmarked minivans grabbing individuals off the street.

"So that was terrifying to hear," Pettibone said.

They had barely made it half a block when an unmarked minivan pulled up in front of them.

"I see guys in camo," O'Shea said. "Four or five of them pop out, open the door and it was just like, 'Oh s***. I don't know who you are or what you want with us.'"

Federal law enforcement officers have been using unmarked vehicles to drive around downtown Portland and detain protesters since at least Tuesday. Personal accounts and multiple videos posted online show the officers driving up to people, detaining individuals with no explanation about why they are being arrested, and driving off.

The tactic appears to be another escalation in federal force deployed on Portland city streets as federal officials and President Trump have said they plan to quell nightly protests outside the federal courthouse and Multnomah County Justice Center that have lasted for more than six weeks.

Officers from the U.S. Marshals Special Operations Group and U.S. Customs and Border Protection's Border Patrol Tactical Unit have been sent to Portland to protect federal property during the protests against racism and police brutality.

In a statement, the U.S. Marshals Service declined to comment on the practice of using unmarked vehicles but said its officers had not arrested Pettibone. The Marshals Service operates under the Department of Justice.

On Thursday, a Department of Homeland Security spokesperson said on background that the agency could confirm Acting DHS Secretary Chad Wolf was in Portland during the day. The spokesperson didn't acknowledge other questions about the arrests. U.S. Customs and Border Protection is part of DHS.

Speaking to NPR's All Things Considered on Friday, Homeland Security Acting Deputy Secretary Ken Cuccinelli acknowledged that federal agents had used unmarked vehicles to pick up people in Portland but said it was done to keep officers safe and away from crowds and to move detainees to a "safe location for questioning."

"The one instance I'm familiar with, they were, believed they had identified someone who had assaulted officers or ... the federal building there, the courthouse. Upon questioning, they determined they did not have the right person and that person was released," Cuccinelli said.

"I fully expect that as long as people continue to be violent and to destroy property that we will attempt to identify those folks," he added. "We will pick them up in front of the courthouse. If we spot them elsewhere, we will pick them up elsewhere. And if we have a question about somebody's identity, like the first example I noted to you, after questioning determine it isn't someone of interest, then they get released. And that's standard law enforcement procedure, and it's going to continue as long as the violence continues."

Customs and Border Protection released a statement Friday about one incident on video, though it did not specify which one. It said its agents approached a person suspected of assaulting federal agents or destroying federal property, but "a large and violent mob moved towards their location" so they moved to a safer place. "The CBP agents identified themselves and were wearing CBP insignia during the encounter. The names of the agents were not displayed due to recent doxing incidents against law enforcement personnel who serve and protect our country."

U.S. Attorney Billy J. Williams, the Department of Justice's chief law enforcement official in Oregon, on Friday called for an inspector general investigation into DHS personnel over reports of two protesters being detained without probable cause.

"What is happening now in Portland should concern everyone in the United States. Usually when we see people in unmarked cars forcibly grab someone off the street, we call it kidnapping," said Jann Carson, interim executive director of the American Civil Liberties Union of Oregon, in a written statement. "The actions of the militarized federal officers are flat-out unconstitutional and will not go unanswered."

A judge has allowed the ACLU to add federal agencies to its lawsuit seeking to limit what law enforcement can do during the protests.

Oregon Attorney General Ellen Rosenblum announced early Saturday morning she would be filing a lawsuit against DHS, the U.S. Marshals Service, the United States Customs and Border Protection, the Federal Protection Service and their agents.

A motion for a temporary restraining order follows the lawsuit. The order seeks to stop federal authorities from unlawfully detaining Oregon residents.

"The federal administration has chosen Portland to use their scare tactics to stop our residents from protesting police brutality and from supporting the Black Lives Matter movement," Rosenblum said in a statement. "Every American should be repulsed when they see this happening. If this can happen here in Portland, it can happen anywhere."

Federal officers have charged at least 13 people with crimes related to the protests so far, while others have been arrested and released, including Pettibone. They also left one demonstrator hospitalized with skull fractures after shooting him in the face with "less lethal" munitions on Saturday, according to video and local reports.

"This is a whole lot of nothing"

Interviews conducted by Oregon Public Broadcasting show officers are detaining people on Portland streets who aren't near federal property. Demonstrators such as O'Shea and Pettibone said they think they were targeted by federal officers for simply wearing black clothing in the area of the demonstration.

O'Shea said he ran when he saw people wearing camouflage jump out of an unmarked vehicle. He said he hid when a second unmarked van pursued him.

Video shot by O'Shea and provided to OPB shows a dark screen as O'Shea narrates the scene. Metadata from the video confirm the time and place of the protesters' account.

"Feds are driving around, grabbing people off the streets," O'Shea said on the video. "I didn't do anything f****** wrong. I'm recording this. I had to let somebody know that this is what happens."

Pettibone did not escape the federal officers.

"I am basically tossed into the van," Pettibone said. "And I had my beanie pulled over my face so I couldn't see, and they held my hands over my head."

Pettibone and O'Shea both said they couldn't think of anything they might have done to end up targeted by law enforcement. They attend protests regularly, but they said they aren't "instigators." They don't spray-paint buildings, shine laser pointers at officers or do anything else other than attend protests, which law enforcement have regularly deemed "unlawful assemblies."

Blinded by his hat, in an unmarked minivan full of armed people dressed in camouflage and body armor who hadn't identified themselves, Pettibone said he was driven around downtown before being unloaded inside a building. He wouldn't learn until after his release that he had been inside the federal courthouse.

"It was basically a process of facing many walls and corners as they patted me down and took my picture and rummaged through my belongings," Pettibone said. "One of them said, 'This is a whole lot of nothing.' "

Pettibone said he was put into a cell. Soon after, two officers came in to read him his Miranda rights. They didn't tell him why he was being arrested. He said they asked him whether he wanted to waive his rights and answer some questions, but Pettibone declined and said he wanted a lawyer. The interview was terminated, and about 90 minutes later, he was released. He said he did not receive any paperwork, citation or record of his arrest.

"I just happened to be wearing black on a sidewalk in downtown Portland at the time," Pettibone said. "And that apparently is grounds for detaining me."

OPB sent DHS an extensive list of questions about Pettibone's arrest including: What is the legal justification for making arrests away from federal property? What is the legal justification for searching people who are not participating in criminal activity? Why are federal officers using civilian vehicles and taking people away in them? Are the arrests federal officers make legal under the Constitution? If so, how?

The DHS spokesperson didn't acknowledge the questions.

"It's like stop and frisk meets Guantanamo Bay," said attorney Juan Chavez, director of the civil rights project at the Oregon Justice Resource Center.

Chavez has worked on litigation surrounding the weeks of protests and helped lead efforts to curb local police from using tear gas and munitions on protesters. He called the arrest by federal officers "terrifying."

"You have laws regarding probable cause that can lead to arrests," he said. "It sounds more like abduction. It sounds like they're kidnapping people off the streets."

Ashlee Albies, a civil rights attorney with the National Lawyers Guild, said Pettibone's detention is an example of intimidation by federal law enforcement, and noted that people have a First Amendment right to demonstrate. She also said law enforcement officials have to follow procedures when they detain someone.

"I would be surprised to see that pulling up in an unmarked van, grabbing people off the street is an acceptable policy for a criminal investigation," Albies said.

''We're going to do what needs to be done''

In a letter released Thursday, Wolf, the acting DHS secretary, said, "Portland has been under siege for 47 straight days by a violent mob while local political leaders refuse to restore order to protect their city."

"A federal courthouse is a symbol of justice," Wolf wrote, denigrating protests against racism in the U.S. criminal justice system as an angry mob. "To attack it is to attack America."

This week, Trump has repeatedly spoken about what he calls lawlessness in the city. He praised the role of federal law enforcement officers in Portland and alluded to increasing their presence in cities nationwide. Speaking to Fox News on Thursday, acting Customs and Border Protection Commissioner Mark Morgan called the protesters criminals.

"I don't want to get ahead of the president and his announcement," Morgan said, "but the Department of Justice is going to be involved in this, DHS is going to be involved in this, and we're really going to take a stand across the board. And we're going to do what needs to be done to protect the men and women of this country."

Early Thursday morning, Portland police tried a new approach to stop the protests. Officers cleared two nearby parks, Lownsdale and Chapman squares, including Riot Ribs, a barbecue stand that had been cooking free food since July Fourth. The city said it was closing the parks for maintenance. By early afternoon, fences had been installed around both parks.

Police arrested nine people during the closure, including three of the people who ran Riot Ribs. They face a variety of charges, including trespassing and disorderly conduct.

Mayor Ted Wheeler's office declined to comment on the latest events involving federal officers but reiterated a statement from earlier this week, saying federal officers should be restricted to guarding federal property.

"We do not need or want their help," Wheeler said. "The best thing they can do is stay inside their building, or leave Portland altogether."

Democratic Sen. Jeff Merkley of Oregon said if Wolf's visit to Portland was to inflame the situation so the president can "look tough," the acting DHS leader should leave.

"Federal forces shot an unarmed protester in the face," Merkley said in a tweet. "These shadowy forces have been escalating, not preventing, violence."

Oregon Gov. Kate Brown similarly called for federal law enforcement officers to leave Portland. She added that Wolf is on a "mission to provoke confrontation for political purposes."

"This political theater from President Trump has nothing to do with public safety," Brown said in a statement. "The president is failing to lead this nation. Now he is deploying federal officers to patrol the streets of Portland in a blatant abuse of power by the federal government."

Copyright NPR 2020.