Federal immigration enforcement agents swept through MacArthur Park in the Westlake District of Los Angeles on Monday morning, prompting a surprise appearance by the mayor.

Residents were outraged after dozens of federal agents marched through MacArthur Park, in one of the city’s most immigrant-heavy neighborhoods. Homeland Security officials said it was an immigration enforcement operation.

A day after federal officers and National Guard troops descended on MacArthur Park in Los Angeles, immigrant residents of the surrounding neighborhood were coming to grips with the operation that local officials said seemed designed to sow fear.