Federal officers and National Guard troops fanned out around a mostly empty Los Angeles park in a largely immigrant neighborhood on foot, horseback and military vehicles Monday for about an hour before abruptly leaving, an operation that local officials said seemed designed to sow fear.

The Department of Homeland Security wouldn’t say whether anyone had been arrested during the brief operation at MacArthur Park. Federal officials did not respond to requests for comment about why the park was targeted or why the raid ended abruptly.

About 90 members of the California National Guard were present to protect immigration officers, defense officials said.

“What I saw in the park today looked like a city under siege, under armed occupation,” said Mayor Karen Bass, who showed up at the park alongside activists.

The operation occurred at a park in a neighborhood with large Mexican, Central American and other immigrant populations and is lined by businesses with signs in Spanish and other languages that has been dubbed by local officials as the “Ellis Island of the West Coast.”

Among those who spoke with Bass were health care outreach workers who were working with homeless residents Monday when troops pointed guns at them and told them to get out of the park.

Photos show federal officers riding on horseback toward a mostly empty soccer field. Heavily armed soldiers and other agents stood guard nearby alongside armored vehicles.

“The world needs to see the troop formation on horses walking through the park, in search of what? In search of what? They’re walking through the area where the children play,” Bass said.

The operation in the large park about 2 miles west of downtown LA included 17 Humvees, four tactical vehicles, two ambulances and the armed soldiers, defense officials said. It came after President Donald Trump deployed thousands of Guard members and active duty Marines to the city last month following protests over previous immigration raids.

More than 4,000 California National Guard and hundreds of U.S. Marines have been deployed in Los Angeles since June — against the wishes of California Gov. Gavin Newsom.