A man will remain in custody on charges that he impersonated a police officer during this past Thursday's protest against U.S. Immigration and Customs Enforcement in downtown Chicago.

A judge on Sunday said it was very concerning that Willie Matthews Jr., 21, was bold enough to go into a crowded area with a loaded gun.

Matthews, of south suburban of Matteson, Illinois, is facing felony charges including false personation of a police officer with a weapon, aggravated unlawful possession of a weapon, and forgery.

Chicago police said officers were on patrol Thursday around 5 p.m. in the 200 block of South Michigan Avenue when they received a radio call about a suspicious man wearing "police identifiers."

A Cook County assistant state's attorney said Chicago police saw Matthews walking up a traffic ramp wearing khaki cargo pants, and a black sweatshirt with the word "police" on its left side and the back.

Prosecutors said Matthews was also wearing a gray backpack with a large black and white police patch affixed.

They said Matthews further wore a gold special police badge without a name or badge number, a pair of black handcuffs, and a black Taurus semiautomatic pistol in a holster.

 However, he wasn't an officer and could not provide valid police credentials, authorities said.

When police approached, prosecutors said, Matthews showed officers a laminated letter.

The letter was allegedly an official document on U.S. Department of State letterhead addressed to Chicago Mayor Brandon Johnson and Chicago police Supt. Larry Snelling, indicating that Matthews was a sworn peace officer. The document claimed Matthews was part of a coordinated effort between the U.S. Department of State and Illinois State Police to observe and report on the behavior of protesters and the police.

Matthews also provided a business card for Operation Menace Society, indicating he was the commanding operations officer. There is not really such thing as Operation Menace Society.

He was taken into custody, at which point officers learned Matthews had a loaded gun.

Prosecutors said he had a valid Firearm Owners Identification card, but was not issued a concealed carry license.

Prosecutors said officers also reached out to federal special agents with the U.S. Department of State Diplomatic Security Service, and found that Matthews' story did not check out. They said agents would not hire or contract anyone to monitor protests.

Illinois State Police say they have never issued a Concealed Carry License to Matthews.

Once again, Matthews will remain detained. His next court hearing is Monday, June 23, in at the Cook County Courthouse in Skokie.

• Chicago