Federal officers on horseback Monday morning cruised a mostly empty MacArthur Park near downtown Los Angeles. Others in fatigues with helmets and long guns showed up, too.

After an hour or so, they cleared out. Defense officials had said some 90 California National Guard members would be there as well in addition to over a dozen military vehicles to help protect immigration officers during a raid at the park.

City officials said they didn’t believe there were any arrests. The Department of Homeland Security wouldn’t say whether anyone had been arrested or what the operation was about.

Mayor Karen Bass, who has repeatedly voiced opposition to the federal immigration raids in L.A, showed up, joining a small crowd that looked on. Activists filmed the officers.

According to Fox News, Bass talked with Border Patrol’s Gregory Bovino, chief of the El Centro Sector.

“I don’t work for Karen Bass,” Bovino told Fox News. “Better get used to us now, ’cause this is going to be normal very soon. We will go anywhere, anytime we want in Los Angeles.”

In a downtown Los Angeles news conference later that day, the mayor responded: “I’m not going to get used to it, because last I checked I was elected to be mayor of this city and that did not include a federal takeover, so either you believe in democracy or you don’t.”

Bass said she believes the operation was meant to intimidate residents, particularly immigrants, from going to work or leaving their homes.

“What I saw in the park today looked like a city under siege or under armed occupation,” she said.

Councilmember Marqueece Harris-Dawson said at the mayor’s news conference that it appeared as if federal immigration authorities staged in the area to film a promotional video for social media.

“What we say to Border Patrol as the council, ‘If you want to film in L.A., you should apply for a film permit like everybody else,’ ” he said. “And stop trying to scare the bejesus out of everybody who lives in this great city and disrupt our economy.”

Jeannette Zanipatin, with the Coalition for Humane Immigrant Rights, saw the brief-but-prominent presence of troops and federal officers at the park.

“I definitely think it’s a source of intimidation,” she said. “We know that the Trump administration is trying to make an example of Los Angeles.”

Activities for summer camps were canceled at the park and children were ushered from the area. Members of a St. John’s Community Health clinic who were providing care to homeless individuals in the park shut down their efforts, Bass said.

By the early afternoon, MacArthur Park had largely returned to calm, though around 30 protesters gathered on Wilshire Boulevard along the park’s north side, waving American and Mexican flags.

Several men with speakers shouted “ICE out of L.A.,” referring to U.S. Immigration and Customs Enforcement. Some passing cars honked in support.

Anna Lopez, a 23-year-old teacher from Lincoln Heights, raised her fist in the air and chanted along with the protesters. She said she knows people who live in the area and came to check in on them.

“The community is strong, and I think everyone is supporting each other,” she said. “We have rights, we still live in a country that has rights. Even though it feels a little less every day, we still have rights and we still have freedom, and we are fighting for them.”

Dog walkers, sunbathers, bicyclists and other park visitors spread out across the grass. The park sits in a densely populated, immigrant-heavy area just west of downtown, and vendors typically sell a wide range of goods on the surrounding sidewalks.

But on Monday afternoon there were fewer vendors than usual, said Joshua Murchison, 30, a caretaker from Westlake hanging out with his dog, Canelo.

“They usually set up down Six Street, they are all just outside, and they have their little stands and stuff — now it’s just all empty,” he said.

“I’m from here … but I still was kind of scared,” he said. “No one was expecting it. No one knew they were going to be coming like that. They came on horses, they came (in) cars. … The whole nine yards. They attacked this whole area.”

Last month, President Donald Trump sent thousands of guard members and active-duty U.S. Marines to Los Angeles in the wake of protests against immigration enforcement raids.

The Associated Press and City News Service contributed to this report.