PORTLAND, Ore. — Police remained tight-lipped here on Monday about a fatal shooting that occurred over the weekend after confrontations between supporters of President Trump and Black Lives Matter counterprotesters, with some local officials fearing the violent incident might beget more mayhem.

The Portland Police Bureau identified the slain man as 39-year-old Aaron J. Danielson, of Portland, and said he had died of a gunshot wound to the chest. Friends of Danielson, who also went by "Jay," said he was a supporter of the far-right group Patriot Prayer. The group alleges that Danielson might have been targeted because he was wearing a hat that bore its insignia.

The incident came after a caravan of Trump supporters — among them, the Patriot Prayer group — made their way through Portland, sparking skirmishes with those who objected to their presence. It again put on edge a city that has seen three months of nightly demonstrations, some of them violent, and sparked political consequences across the country.

Trump had on Sunday retweeted a video showing his supporters driving into Portland, adding the message, “GREAT PATRIOTS!” On Monday, he said the Departments of Justice and Homeland Security would create “a joint operations center to investigate the violent left-wing civil unrest.” Noting that 100 people in Portland have already been arrested on federal charges, the president said the “violence and destruction that we’ve seen in recent weeks and months has occurred in cities exclusively controlled and dominated by the Joe Biden party.”

Law enforcement officials, including Trump’s own attorney general and Justice Department, have attributed the violence at some nationwide demonstrations to a wide array of political actors, including those on the right. Patriot Prayer has a history of organizing rallies in the Pacific Northwest that spark conflict. The stated aim of Patriot Prayer, organized in 2016 to bring pro-Trump rallies to liberal bastions, is to “liberate the conservatives on the West Coast.” 

Even though Saturday’s shooting was captured on video, the precise details of what happened — and why — remain unclear.

In one video posted online, men can be heard shouting, followed in rapid succession by the sound of something spraying and then two gunshots.

Justin Dunlap, a lighting technician from nearby Vancouver, Wash., who recorded the widely circulated video and broadcast it live on Facebook, previously told The Washington Post he heard yelling and saw mace being sprayed. Then gunshots rang out.

Dunlap, 44, said that when the gunshots were fired, “the guy who had sprayed the bear mace turned and took three or four steps and then went face down. While he was doing that, the two that he had bear-maced ran back in my general direction and kind of went around the corner.”

In a taped interview posted online, Chandler Pappas, who said he was with Danielson during the shooting, said whoever fired the shots “recognized our Patriot Prayer hats,” and just before gunfire rang out, he heard someone say, “We’ve got a couple of ‘em right here. Pull it out. Pull it out.”

“It didn’t even register that somebody was pointing a gun at us until the shots went off,” Pappas said. “Jay’s dead because he believed something different than them.”

Pappas told The Washington Post that Danielson was “killed in cold blood” but did not provide other details.

Joey Gibson, the founder of Patriot Prayer, said that the incident occurred after the Trump caravan had broken up and that Pappas had told him a similar account to what he said in the online interview.

Authorities have not released a detailed account of the incident.

A night of relative peace unfolded the day after Saturday’s mayhem, though officials still said they were worried about possible retaliation.

“For those of you saying . . . that you plan to come to Portland to seek retribution, I’m calling on you to stay away,” Portland Mayor Ted Wheeler said Sunday. “You of course have a constitutional right to be here, but we’re asking you to stay away and work with us to help us de-escalate the situation.”

The protesters who had gathered at Laurelhurst Park for the city’s nightly protest numbered around 100 on Sunday. It was smaller than past marches in this city, but by nightfall, police said, around 150 had amassed to gather in front of the Penumbra Kelly city building, which houses some police services.

Fran Bittakis, founder of Snack Bloc, a mutual aid group that provides water, snacks, medical supplies and protective equipment to demonstrators, said that in the wake of Saturday’s events, further escalation felt inevitable. She was among those who had gathered at the park.

“People should be scared,” she said. “Nobody wanted anyone to get killed. I think the thing is that now that it is someone on that side of things, it’s a very retaliatory [fear] — that’s what we are all feeling that can happen.”

That fear has also encouraged the protesters to become more vigilant about facing down the threats.

“We don’t have vests, we don’t have the gear that they have, we haven’t been training in military tactics and theory,” she said. But the fear ramps up every weekend of outside groups coming into town to stir things up, and that concern had grown further after Saturday’s violence.

The Portland shooting came on the heels of a violent incident during unrest in Kenosha, Wis., over the police shooting of 29-year-old Jacob Blake. Amid demonstrations there, a 17-year-old wielding an AR-15-style rifle shot and killed two men and injured a third, authorities allege.

Local officials and residents were preparing for Trump’s planned visit to the city on Tuesday, and some said they wished the president would delay his trip, citing the city’s need to heal after the recent chaos. Trump on Monday suggested that the 17-year-old facing murder charges in Kenosha was forced to defend himself.

“You saw the same tape I saw, and he was trying to get away from them I guess, it looks like, and he fell, and then they very violently attacked him. And it’s something we’re looking at right now and it’s under investigation,” the president said. “I guess he was in very big trouble — he probably would have been killed — but it’s under investigation.”

After the shooting, Oregon Gov. Kate Brown (D) issued a statement denouncing “the right-wing group Patriot Prayer and self-proclaimed militia members” who she said “drove into downtown Portland . . . armed and looking for a fight.”

Brown also released what her office said was a plan to bolster the law enforcement response in Portland. Under the plan, the Oregon State Police would dispatch personnel so the Portland police can focus on arresting and charging “those engaging in violent acts,” Brown’s office said in the statement.

The local district attorney will prosecute offenses such as arson and physical violence, her office said, while the sheriff’s office would make sure there is jail space to hold people “booked for violent behavior.” Brown said other local and federal officials would also help.

On Sunday, activists chanted and yelled taunts at police as they blared loud music and gathered in the street. Police declared an unlawful assembly about 10:40 p.m. Officers bull-rushed activists — pinning down several of them — fired pepper balls and made arrests. It was the first of several such responses by police Sunday, who were aided by an additional phalanx of Oregon State Police after Saturday’s clashes. The Portland Police Bureau said it ultimately arrested 29 people after declaring an unlawful assembly in the area.

The arrests seemingly came at random and targeted anyone who was seen violating the unlawful assembly order by remaining in the street. Demonstrators were mostly held for alleged disorderly conduct and interfering with police officers. But the added police from the state level led to some coordination issues and confusion.

Gabriel Trumbly, 29, a paralegal who runs a photography business and has been documenting the protests, was abruptly shoved to the ground, handcuffed and held before being released less than an hour later. Trumbly, wearing gear clearly marked “PRESS,” was told he had been interfering. His release came after Portland police at the site asked state police why he had been arrested.

“I was standing for a minute and a sergeant came over was like, ‘Where’s the press guy? You’re getting out of here. Sorry about this,’ ” Trumbly recalled.

Trumbly said he saw a line of about 25 people inside waiting to be processed. It was calmer than the scenes outside.

“They definitely slammed my head to the ground, but the helmet probably helped me on that one,” he said.

Devlin Barrett, Mark Berman and Julie Tate contributed to this report.