In a massive show of force, federal law enforcement officers fired rubber bullets and chemical gas at peaceful protesters outside the White House on Monday evening as President Trump appeared in the Rose Garden to threaten the mobilization of “thousands and thousands of heavily armed soldiers” to quell “lawlessness” across the country.

Hundreds of protesters were pushed away from Lafayette Square, where they were protesting the police killing of George Floyd, by the National Guard, U.S. Park Police and Secret Service. The ambush began half an hour before the city’s newly imposed curfew of 7 p.m. went into effect. When the crowds were cleared, the president walked through the park to visit the historic St. John’s Episcopal Church, which had been set on fire Sunday.

The sudden use of force left early protesters bruised, bleeding and in shock. Although the night would ultimately end with a spattering of smashed windows and vandalized businesses, the scene in front of the White House when federal law enforcement descended was far from the “violent mobs” Trump described in his speech. The gathering was smaller and calmer than previous evenings, with people dancing and singing to a woman playing a guitar instead of knocking over barricades.

Some demonstrators planned to disperse at 7 p.m., the curfew D.C. Mayor Muriel E. Bowser (D) had imposed in hopes of avoiding another destructive night. But the appearance of the National Guard and mounted U.S. Park Police brought the most aggressive law enforcement response yet. The FBI, Bureau of Alcohol, Tobacco, Firearms and Explosives, Drug Enforcement Administration, U.S. Marshals and Bureau of Prisons were all involved in the federal response, according to a Justice Department spokeswoman.

Attorney General William P. Barr also appeared in the park, where protesters shouted at him and chanted his name with expletives.

As they did, the law enforcement officers began advancing. With shields that said “military police,” they stood in a line, shoulder to shoulder, and moved forward every few minutes. When they knelt — as officers across the country have been doing to show solidarity with demonstrators — the crowd cheered. But protesters soon realized they were kneeling only to put on gas masks.

Minutes later, law enforcement officers fired at the gathered ­masses. Rubber bullets hit protesters who were standing atop a bathroom that had been burned the night before. One person fell from the structure. People ran down 16th Street, trying to flee the chemical canisters spewing gasses that left them coughing. Some stopped running when they started vomiting. Others yelled “Walk! Walk!” in attempts to avoid a stampede.

“They flushing us out,” one protester told another.

In the hours that followed, the impact of the officers’ agression kept protestors away from the White House. They instead scattered across the city in droves, turning the evening into a cat-and-mouse game for D.C. police officers trying to encircle them. When protestors found themselves outnumbered, they were asked to sit so they could be arrested one by one, a process far more orderly than the chaos in Lafayette Square.

As the arrests continued, Bowser took to Twitter condemed the federal agencies’ actions.

“A full 25 minutes before the curfew & w/o provocation, federal police used munitions on peaceful protestors in front of the White House, an act that will make the job of @DCPoliceDept officers more difficult. Shameful!”

Arlington County officers who were supporting Park Police at Lafayette Square were ordered to leave downtown after county officials realized they had been a part of what they called a presidential publicity stunt.

“The mutual aid agreement is not put in place to allow for a blatantly political act,” said County Manager Mark Schwartz. “Crowd control is a far cry from assisting someone to stand in front of a church.”

White House spokesman Judd Deere defended the federal actions, saying “the perimeter was expanded to help enforce the 7 p.m. curfew in the same area where rioters attempted to burn down one of our nation’s most historic churches the night before. Protesters were given three warnings by the U.S. Park Police.”

After the path from the White House to St. John’s Episcopal Church was cleared, Trump and a large entourage, most of them not wearing masks, walked through Lafayette Square to the historic church. The president held up a Bible for several seconds. Asked by a reporter whether it was his Bible, he said, “It’s a Bible.”

Mariann Budde, the Episcopal bishop of Washington, said she had no idea “that they would be clearing [the area] with gas so they could use one of our churches as a prop, holding a Bible, one that declares that God is love and when everything he has said and done is to inflame violence.”

“I am outraged,” Budde said.

Her anger was shared by demonstrators, as they tried to stop their eyes from stinging and argued about what to do now that they had been pushed away from the White House.

D.C. protests organized in reaction to George Floyd’s death continued on May 31. Multiple fires broke out, including one at historic St. John’s Church. (The Washington Post)

“If we die here today, it’s not worth it today, bro,” one man told another. “It’s after 7, they can do whatever they want to you. There are no rules.”

Nsidebe Eka, 19, ran back toward Lafayette Square, looking for a set of lost keys. Her family didn’t want her to go to the protest, but she said she was tired of sitting on the sidelines.

“We had a peaceful protest and they still did all that,” she said. “They don’t love us, they don’t [care] about us, and it’s because we’re black.”

Sarah Rosner, a 37-year-old Dupont Circle resident and lead bartender at the flagship Four Seasons in the District, was recovering from being pushed to the ground by an officer, she said.

“You got to get out of here, you can’t hit your head again,” Rosner’s friend told her.

Protesters who lingered were met by dozens of D.C. police officers in riot gear and announcements over the loudspeaker of their police cruisers: “Attention: You are subject to immediate arrest. You are in violation of the mayor’s order.”

They spread out across the downtown streets, and then found each other again, trying to stay on the move to avoid being encircled.

Some headed to the Mall, where the National Guard was stationed around the World War II and Lincoln memorials.

“We are going to be stuck in there,” a black woman leading the group said as some tried to head to the Martin Luther King Jr. Memorial. “It’s a trap.”

The DEA, the Federal Protective Service and the FBI blocked roads and areas that attracted looting in previous nights.

Barr made an appearance again, walking downtown with Defense Secretary Mark T. Esper and Gen. Mark A. Milley, chairman of the Joint Chiefs of Staff.

At Thomas Circle, protesters climbed on top of the towering statue of Maj. Gen. George Henry Thomas. But only for a moment: Police sirens began wailing as police cars rushed down Massachusetts Avenue, and the protesters — mistakenly thinking officers were rushing to arrest them — quickly hopped down and began running.

Dozens walked together up 14th Street NW, the site of some of the worst rioting in 1968, but now one of D.C.’s most expensive neighborhoods. They moved past boarded-up shops and restaurants, past Le Diplomate, Room and Board, Shake Shack and Lupo Verde.

“We are here for justice,” a young black man shouted as others knelt. “We ain’t here for no injustice. Say his name!”

“George Floyd,” the crowd roared.

Some people appeared on the balconies of apartment buildings to cheer or hold up “Black Lives Matter” signs.

As police converged on protesters gathered on Swann Street, a resident let dozens of them take shelter in his home.

Rahul Dubey was sitting on his porch when police started pushing the group down the street and firing chemicals, creating a frantic bottleneck that sent them scrambling for safety.

“It was a human tsunami,” he said. “I was hanging on my railing yelling, ‘Get in the house! Get in the house!”

Soon, there were more than 100 people in his house, the 44-year-old businessman said. They filled all three floors of his home and spilled out into his backyard. He promised to let them stay “as long as it takes.”

In empty parts of the city, lone protesters wandered, looking for the crowds. Tristian Taylor, 22, came in with five friends from Bowie, Md., to join the protests, despite the curfew.

“We’re not worried about it,” Taylor said. “Malcolm X said ‘by any means necessary.’ We’re trying to resurrect the dream.”

Law enforcement, too, were looking for crowds.

Krista Brown, 26, attempted to record police activity after a unit of bicycle officers swept along T Street NW as police appeared to encircle protesters. Officers threatened to jail her as she challenged why they were interrupting a peaceful protest.

“Ma’am, do you want to go to jail?” at least three officers asked her.

After several minutes she walked away. As a white person, she said, she wanted to step forward in a way that people of color might not be able to.

“I tried to walk up and record it and they told me if I did, I would be arrested,” Brown said. “They have militarized this whole scene I think to make a point of cracking down.”

At I and 16th Street, D.C. police formed lines that sealed off streets around a group of about 30 protesters, until they were surrounded. For 20 minutes or so, the protesters remained on foot, chanting and waving signs, as police backed in vans to take them away.

Then, after the group of protesters was directed to sit on the street, the police led them one by one to the vans.

Most complied peacefully with a methodical process. Shoes were removed, fingerprints taken, and belongings were bagged. Police removed a can of black spray paint from a backpack that belonged to a young white man in T-shirt and khaki shorts. A young woman went limp on the street and four officers carried her closer to the van; later she got up and walked.

Another young man — who declined to identify himself — sprawled on the street and kept up a steady patter aimed at the police, saying he once looked up to them as heroes but not anymore.

When they picked him up because he refused to move, he shouted, “I am not an animal.”

As similar assembly lines of arrest played out across the city, those who remained on the streets seemed more interested in looting than protesting. Around 10 p.m., they began smashing windows on New Jersey Avenue, along with Fourth and Seventh streets. Chinatown businesses including Dunkin’, Legal Seafood and Bibipop had windows destroyed.

One man pried the boards off a CVS and dozens sprinted inside yelling “Food!” He emerged moments later with arms bulging with soft drinks and snack packets.

The groups left on the street were trailed by hundreds of law enforcement officials, who fired flash grenades and sent protestors sprinting away. The vandals would run for a block or two, then regain confidence and return to looting, only to inspire another rush by police.

As the window of a police vehicle was smashed, a military or law enforcement helicopter descended on Chinatown, flying almost as low as the rooftops. Broken glass and branches were sent flying as protestors screamed and ran.

Marley Coehins, 21, said she was pushed over in the scramble and had to be helped back to her feet. “They were busting windows for nothing,” she said of the vandals and looters as she rested on the corner of Eighth and E streets NW. “Then the broken police window set them off.”

But Coehins said she would not be deterred.

“We’re going back,” she said, turning to her friend as they headed in the direction of the moving protest.

By midnight, the city was far quieter than the three previous nights. In front of the White House, scores of Secret Service and military police officers sat on the curb, with no use for their shields or helmets.

On Swann Street, the house of the man who had taken in more than 100 protestors was still full. With the streets blocked off by law enforcement, people were afraid to leave. As the standoff stretched past midnight, Dubey worried about the protesters getting hungry. He said he had five pounds of ground beef he could feed them, but not much more.

When Dubey asked police for assistance, he said, he told them to go back inside or he would be arrested.

“These kids,” he said, “want to go home.”

Sarah Pulliam Bailey, Rachel Chason, Emily Davies, Peter Jamison, Dan Lamothe, Michael E. Miller, Hannah Natanson, Fenit Nirappil, Perry Stein, Clarence Williams and Matt Zapotosky contributed to this report.