PORTLAND, Ore. >> The mayor of Portland, Oregon, and President Donald Trump engaged in a real-time argument Sunday as the president sent a flurry of critical tweets about Ted Wheeler as the mayor was holding a press conference about the fatal shooting of a right-wing supporter in his city the night before.

After Trump called Wheeler, a Democrat, a “fool” and blamed him for allowing violence to proliferate in the liberal city, the visibly angry mayor lashed out at the president, addressing him in the first person through the TV cameras.

“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. Wouldn’t that be a message? Donald Trump and Ted Wheeler working together to help move this country forward. Why don’t we try that for a change?”

The testy news conference followed a chaotic and volatile 24 hours in Portland that began when a caravan of about 600 vehicles packed with Trump supporters drove through Portland and was met with counterprotesters. Skirmishes broke out between the groups and, about 15 minutes after the caravan left the city, 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 between Trump supporters and counterprotesters in Portland, which has 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.

Trump and other speakers at last week’s Republican National Convention evoked a violent, dystopian future if Democratic presidential hopeful Joe Biden wins in November and pointed to Portland as a cautionary tale for what would be in store for Americans.

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

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 in the liberal city long before the national outrage over Floyd’s death sparked more than three months of protests here.

Portland has seen nearly 100 consecutive nights of Black Lives Matter protests and many have ended with vandalism to federal and city property, including police precincts, a county jail, 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, as agents lobbed tear gas canisters and pepper spray at the crowds and some protesters tossed fireworks at the agents and shined lasers in their eyes.

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 as they try to de-escalate tensions and braced for what promised to be another night of violence. A protest was planned for Sunday night on the city’s east side.

Late Sunday Oregon Gov. Kate Brown released details of a plan to address the violence in Portland while protecting free speech. She said the district attorney’s office in Multnomah County, which includes Portland, 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 Oregon State Police will return to Portland to help local police and nearby law enforcement agencies will also be asked to assist.

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. “They are still assembling the facts. This is not the time to get hotheaded because you read something on Twitter that some guy made up in his mother’s basement.”

Acting Homeland Security Secretary Chad Wolf blamed local officials for failing “to protect their communities.”

“I’m asking Portland officials, so that’s the mayor, that’s the governor and that’s local law enforcement, to do their job to address any violent activity that is occurring in their streets,” Wolf told CBS’ “Face the Nation.”

Wolf said the federal government was prepared to send agents to Portland and other cities to protect federal buildings and assist police.

Lovell and Wheeler said they had no plans to request National Guard troops but the city is seeking assistance from the sheriff’s department and Oregon State Police.