By GILLIAN FLACCUS

PORTLAND, Ore. (AP) — State Police will return to Portland to help local authorities after the fatal shooting of a man following clashes between President Donald Trump supporters and counter-protesters that led to an argument between the president and the mayor over who was to blame for the violence.

Protesters were back on the streets for a demonstration Sunday night outside a public safety building. Police declared an unlawful assembly and arrested 29 people. Two of those arrested had handguns and others had knives and at least one had an expandable baton, police said.

Many in the group wore helmets, gas masks, goggles, and external armor. Police said some carried shields and reflective squares used to reflect police lights back toward officers. Some threw rocks, eggs, and other items at officers and police vehicles.

After Trump called Ted Wheeler, a Democrat, a “fool” and faulted him for allowing mayhem to proliferate in the liberal city, the visibly angry mayor lashed out during a Sunday news conference, addressing the president in the first person.

“That’s classic Trump. Mr. President, how can you think that a comment like that, if you’re watching this, is in any way helpful? It’s an aggressive stance, it is not collaborative. I certainly reached out, I believe in a collaborative manner, by saying earlier that you need to do your part and I need to do my part and then we both need to be held accountable,” Wheeler said.

“Let’s work together…Why don’t we try that for a change?”

Trump on Monday tweeted: “Portland is a mess, and it has been for many years. If this joke of a mayor doesn’t clean it up, we will go in and do it for them!” He did not describe any specifics on how that would happen.

The testy news conference followed a chaotic 24 hours that began Saturday evening when a caravan of about 600 vehicles packed with Trump supporters drove through the liberal city and was met with counterprotesters. Skirmishes broke out minutes later a supporter of the right-wing group Patriot Prayer was fatally shot.

Patriot Prayer founder Joey Gibson identified the victim as Aaron “Jay” Danielson. He called the victim a “good friend,” but provided no further details. Danielson apparently also went by the name Jay Bishop, according to Patriot Prayer’s Facebook page.

“We love Jay and he had such a huge heart. God bless him and the life he lived,” Gibson said in a Facebook post. Trump retweeted the victim’s name and wrote, “Rest in peace Jay!”

It wasn’t clear if the shooting was related to the clashes, which have become a flashpoint in the national Black Lives Matter protests since George Floyd was killed in May and an increasing centerpiece in Trump’s law-and-order re-election campaign theme.

Police have released little information about the fatal shooting and Chief Chuck Lovell said Sunday that investigators are still gathering evidence. Earlier, the agency released a plea for any information related to the killing, including videos, photos or eyewitness accounts.

Late Sunday, Gov. Kate Brown released details of a plan to address the violence while protecting free speech. She said the district attorney’s office will prosecute serious criminal offenses and the sheriff’s office will work with other agencies to hold people arrested for violent behavior and ensure there is adequate jail space.

Also, Brown said State Police will return to Portland to help local police, and nearby law enforcement agencies will also be asked to assist.

“We all must come together—elected officials, community leaders, all of us—to stop the cycle of violence,” the Democrat said in a statement.

Trump and other speakers at last week’s Republican National Convention evoked a violent, dystopian future if Democrat Joe Biden wins in November and pointed to Portland as a cautionary tale.

Patriot Prayer is based in Washington state and was founded in 2016. Since early 2017, its supporters have been periodically coming to Portland to hold rallies for Trump, ratcheting up tensions long before the national outrage over Floyd’s death.

Portland has seen nearly 100 consecutive nights of Black Lives Matter protests and many have ended with vandalism to federal and city property, including the federal courthouse and City Hall. In July, Trump sent more than 100 federal agents from the U.S. Department of Homeland Security to safeguard federal property — a move that instead reinvigorated the protests.

Thousands of people clashed with the federal agents each night for two weeks.

Those agents withdrew July 31 but smaller nightly protests have continued in pockets of the city. More than 600 people have been arrested since late May.

On Sunday, Portland authorities urged people to stay away from the downtown.

Trump earlier Sunday appeared to be encouraging his supporters to move into Portland in the wake of the shooting. After the shooting, the president shared a video of his supporters driving into Portland and called those in Saturday’s caravan “GREAT PATRIOTS!”

Wheeler begged those who wanted to come to Portland to “seek retribution” to stay away.

“If you’re from out of town and you’re reading something on social media — if you’re reading any facts on social media — they’re probably wrong because we don’t have all the facts yet,” Wheeler said. “This is not the time to get hotheaded because you read something on Twitter that some guy made up in his mother’s basement.”