The U.S. Department of Homeland Security says a protester at the "No Kings" rally in Chicago should face criminal charges for allegedly calling for U.S. Immigration and Customs Enforcement agents to be shot.

Sources told CBS News Chicago that the case has been referred to the FBI for investigation into the statements made in a video posted by DHS to their social media. CBS News Chicago has also not been able to identify the original source of the piece of video that was edited into DHS's media.

In the snippet that is part of a video posted by DHS, a man can be heard saying "You gotta grab a gun. You gotta turn around the guns on this fascist system. These ICE agents gotta get shot and wiped out."

DHS claims the video was taken during the Chicago "No Kings" protest in Grant Park Saturday, and the agency characterized the man's statement as calling "for the cold-blooded murder of ICE agents."

The FBI Chicago Field Office said they cannot comment "on the existence" of an investigation, but a source told CBS News Chicago that it's currently under review.

The remainder of the video shows theatrical imagery of unidentified, heavily armed law enforcement members entering various buildings, followed by images of people in handcuffs and the text "Don't try it."

The Chicago "No Kings" event was peaceful. Organizers estimated as many as 250,000 people flooded downtown, and Chicago police said no arrests were made in connection with either the rally or the march.

CBS News Legal Analyst Irv Miller said there's a delicate line between free speech and threats that can be prosecuted.

"Frankly, it boils down to the specific facts of what he said, not just the isolated remarks, but also the entire speech," he said.

Miller said investigators will consider whether the man is in violation of the "fighting words" exemption to the first amendment right to freedom of speech.

"If you are inciting somebody to enter into a fight, that's more than just words. You're now communicating your words into action, and action could be a violation of criminal statutes," Miller said.

CBS News Chicago is not identifying the man in the video because at last check there have been no charges filed in this case. Social media posts indicate he was an employee of Wilbur Wright College.

CBS News Chicago reached out to City Colleges of Chicago and a spokesperson confirmed the man had worked there in the past, but now "the individual is not employed by Wilbur Wright College or any affiliated colleges. Our college system does not tolerate violence nor incitement under any circumstances."

City Colleges of Chicago did not comment on the circumstances surrounding the man's departure from Wilbur Wright.

When CBS News Chicago reached out to DHS, they referred us to the Department of Justice for any further comment on this case. We did as asked, and have not yet heard back from DOJ.