Man charged with possession of dangerous weapon in hours-long standoff at Chicago federal building

Suspect entered Dirksen Federal Building armed with knife, federal officials say

ByMark Rivera and Barb Markoff, Christine Tressel and Tom Jones WLS logo
Friday, July 25, 2025
Man charged in hours-long standoff at Chicago federal building

CHICAGO (WLS) -- A man is now facing a felony charge for allegedly wielding a knife during a standoff at a Chicago federal building, the ABC7 I-Team has learned.

A standoff at the Dirksen Federal Building downtown ended after roughly nine hours Tuesday night, officials said.

Just before 8 p.m., federal agents were seen rushing toward the man who had been standing in the building's lobby since about 11 a.m., with a knife.

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The man was on the ground surrounded before being put on a stretcher.

He has now been identified as 38-year-old Mario Santoyo of Chicago. The suspect has been charged with felony "possession of a dangerous weapon in a federal facility with intent to use the weapon in the commission of a crime," the U.S. Attorney's Office announced.

READ MORE | Process of protection behind safe outcome of hours-long standoff at Dirksen Federal Building

Santoyo allegedly entered the building and "asked to speak with the FBI about 'gangsters' or 'gangbangers' who were trying to kill him," according to a news release.

"The defendant created a dangerous situation for himself, law enforcement, and the thousands of federal employees and members of the public inside the Dirksen Building," U.S. Marshal LaDon A. Reynolds said in a statement. "The standoff in this case was peacefully resolved thanks to the courage and professionalism of the law enforcement officers from the U.S. Marshals Service and FBI. I am deeply appreciative of this U.S. Attorney's strong partnership with the U.S. Marshals Service and for his strong leadership in choosing to bring a felony charge to hold the defendant accountable for his intolerable actions."

Santoyo was hospitalized after the standoff, and he appeared in federal court Friday afternoon.

A judge ordered him to be held in federal custody.

Santoyo will be back in court next Thursday for his detention hearing.

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