Some 10 Department of Homeland Security agents descended on an apartment building between Mission Street between 18th and 19th Thursday morning to execute a federal search warrant, and took one Latino man, named Brian, into custody.

The Homeland Security Investigations agents, outfitted in bulletproof vests, repeatedly said it was “not an immigration matter” and there were no collateral arrests — meaning no undocumented residents were taken into custody during the arrest of the suspect. It’s unclear if Brian is undocumented.

One of the agents on the scene explained to a woman that her son was being transported to 450 Golden Gate Ave., a federal building downtown. The agents said the suspect could be out on bail in the next couple of days. The agents took his car and told his mother to bring her son’s passport. “That’s all he needs,” the agent said.

Another agent on the scene told the woman that her son could have an initial court appearance today.

One of the agents told the woman that her son tried to flee out of a back window of his apartment on Mission Street near 19th Street. “But he’s okay,” the agent said.

Richard Rocha, a spokesperson for the Department of Homeland Security’s San Francisco office, told Mission Local that he had no details on the arrest, but said that Immigration and Customs Enforcement conducts operations every day throughout the city and “routinely executes criminal search and arrest warrants.”

Rocha said that these operations are not about a person’s immigration status, but abut enforcing 400 criminal statutes. According to its website, the federal agency is tasked with investigating “cross-border criminal activity.”

By around 10 a.m., agents were filtering in and out of a small entrance at the suspect’s apartment. Dogs barked from inside the entrance, and the mother continued to ask in Spanish, “How much longer?”

The agent unloaded equipment out of unmarked cars — a dirty and beat-up minivan and SUV.

“I have never seen anything like this,” said a 27-year-old man named Omar, who said he was a resident of the building and the cousin of the man who was taken into custody. “I have no idea what’s going on.”

He said he rushed over after he got a call from his aunt, the mother of the man taken who was arrested.

He said around six people live in the building, in about four rooms. Agents on the scene said the search warrant would take hours.

“It’s really messed up and she (the mother) doesn’t know what’s going on,” said Leticia Arce, an employee with Causa Justa, a housing rights organization, who was translating for the woman. “It’s important to at least have someone speaking Spanish for her.”

The mother declined to talk to reporters.