The warning came three hours before climate activist Tim DeChristopher's prison sentence turned a downtown thoroughfare into chaos.
"There will be something else to watch for," Krista Bowers predicted as midday peace anthems strummed in the background.
By rush hour less than two hours after DeChristopher's sentence was announced police arrested two dozen people who locked themselves together with plastic ties and blocked traffic at the bustling intersection of 400 South and Main Street, including stopping a TRAX train.
Some were escorted away by police. One was carried.
Horns blared some in anger, some in solidarity while a string of southbound cars made illegal U-turns over the train tracks on Main Street. Dozens of protesters, who had attended the daylong Peaceful Uprising rally, poured onto the street, cheering and chanting during each arrest.
Salt Lake City's Chelsea Satre, arrested for her role in the demonstration, tried twice to get up and run but was pushed down by police. Officers then bound her ankles.
"I thought they were going to break my arm," she said about being carted off the TRAX line, legs bent in protest. "They were a little excessive. I'm sure it might be a night in jail and a nice fine. Tim DeChristopher made a stand for a mass-global crisis. The least we can do is stand with him."
Minutes before her arrest, an angry mob of commuters abandoned their southbound train and stormed through the throngs, walking a block to the courthouse station.
"Get out of the way," yelled Murray resident D.J. Myrup. "We want to go home from work. It's a bunch of crap."
Crammed onto the courthouse TRAX platform, dozens of downtown workers called home on cellphones to complain about the scene. "We're pissed," said Murray's Janie King, annoyed by the hours of song that had been audible from her law office.
"They just want to sing and do their thing because they don't have jobs. We all have jobs and want to get home to our families."
DeChristopher supporter Ryan Pleune, dressed in a black suit, walked over to apologize using a megaphone but was shouted down. "You should be arrested," screamed Brooke Ellsworth, of South Salt Lake. "We all have jobs and children."
A mocking chant of "free the train" ensued.
And yet, the Utah Transit Authority said none of the spats became serious enough to reach the agency's attention.
"I'm sure there were people that were frustrated trying to get home after work," UTA spokesman Gerry Carpenter said, "but there were no reports of any incidents."
By 6:30 p.m., protesters cleared from the intersection, regular traffic resumed. Police charged 26 protesters with unlawful assembly, failure to disperse and blocking a roadway. Those demonstrators were expected to be released from jail late Tuesday or early Wednesday.
Other than refusing to leave the roadway, Salt Lake City Police Chief Chris Burbank said protesters "were very respectful of the officers."
The courthouse setting turned chaotic just minutes after tearful DeChristopher backers learned of their folk hero's fate.
"This is not justice," a man yelled as the crowd was told similar rallies were being staged in 19 other cities.
An emotional Henia Belalia took the megaphone to announce, "Our hearts are broken today. Consider this the spark that will unite this movement."
With that, supporters rushed the steps to block both courthouse entrances, wrists quickly bound together with plastic ties.
"He's not coming out. They took him away and he didn't hurt anyone," Ashley Anderson belted. "This is corrupt."
When Anderson tried to block a second entrance, fist in the air, a half dozen federal officers pushed him back. "Don't do this," said one officer, who refused to give his name. "You guys have been cool the whole time."
Later, the federal and local officers backed off, watching the sit-in through dark sunglasses from 50 feet away.
On the other steps, former Bureau of Land Management employee Skip Edwards took his turn at the megaphone. "I took Judge Benson down Westwater Canyon years ago," he said. "That guy obviously has no respect for wilderness."
Later, Edwards implored the crowd not to sit idly by. "If that's all we do is stand in the streets, then our time here's a total waste."
In a quiet moment before DeChristopher's sentencing, Peter, Paul and Mary musician Peter Yarrow said the location of the land leases was so near to national parks and sensitive land that it "intensified the sense of absurdity" of the conviction.
"This will be the ignition point for turning complacency into real awareness," he said, sipping a milk shake. "He really is the Rosa Parks of this movement."
The rally began at noon with a modest turnout, but ballooned to 150 by the scheduled 3 p.m. court time. After speeches and several Bob Dylan songs at Exchange Place, the crowd, wearing orange Peaceful Uprising sashes, marched to the courthouse steps.
"We're here for the whole earth and the air and the mountains and the water," Salt Lake City's Cherise Udell told her young daughters during the procession. She said she explained to them that DeChristopher was akin to a Disney character beating back a villain.
For nearly two hours, the crowd waved banners, beat drums, sang and often chanted, "Let's tell the whole world that we want climate justice."
Dark clouds hung over the courthouse for much of the day, then released a light smattering of rain.
Waiting for the sentence, Salt Lake City's Inga Chapman said she expected jail time but predicted it wouldn't silence DeChristopher. "I expect he'll have a voice from there," she said. "People have been very effective going to jail."
Tweeting the news, capital resident Cori Redstone said supporters were less surprised by jail than they were that DeChristopher was immediately detained. "It's just another act of intimidation by the federal government," she said. "This sentence was completely out of hand, unjustified and overreaching."
Within minutes of that tweet, the intersection exploded into civil disobedience.
Jason Bergreen, Nate Carlisle and Cimaron Neugebauer contributed to this report