PORTLAND, Ore. — The mayor of Portland 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 news 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 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 back-and-forth 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.

Joey Gibson, founder of Washington state-based Patriot Prayer, 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!”

Police said the man was shot in the chest. It’s unclear who shot him

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 May 25 and an increasing centerpiece in Trump’s law-and-order reelection campaign theme.

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 witness accounts.

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.

Those agents withdrew July 31 but smaller nightly protests have continued in pockets of the city.

On Sunday, Portland authorities urged people to stay away from the downtown as they try to deescalate 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.

Trump earlier Sunday appeared to be encouraging his supporters to move into Portland. 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 state police.

Wheeler, who is running for a second term and is also the police commissioner, also rejected a call for his resignation made Sunday by a coalition of civil rights and protest groups.