CHICAGO (WLS) — After almost nine hours, a standoff concluded Tuesday night at the Dirksen Federal Building. Authorities have yet to reveal the suspect’s name or any possible motives, even though this incident resulted in a significant lockdown of the downtown Chicago courthouse for most of the day.

Federal investigators remained silent on Wednesday, offering no insight into what charges, if any, will be filed.

In the aftermath of the lockdown, the ABC7 I-Team consulted with federal law enforcement experts concerning the measures taken to safeguard both the public and the suspect. This individual, according to officials, prompted a full evacuation of the busy Dirksen and halted court proceedings for several hours on Tuesday.

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In the heart of downtown, there was commotion and confusion at one of the most secure federal facilities in the city.

The man, whose identity remains unknown, entered the Dirksen Federal Building on Tuesday just before 11 a.m. Dressed in khakis and a blue-collared shirt, he was seen holding a knife to his throat.

His tan backpack with the word “MIAMI” stitched into it was likely what prompted a response from the bomb squad, federal law enforcement sources told the I-Team.

ABC7 law enforcement expert and retired U.S. Secret Service Agent Derrek Mayer said FBI negotiators, U.S. Marshals and other law enforcement responding to the Dirksen on Tuesday played it by the book, relying on their training and evacuating the entire building as part of a larger strategy.

“You don’t know if he has any accomplices,” Mayer said. “They had to make sure everybody in the vicinity, everybody in the building, was safe… Worst case, it could be a diversion.”

The person at the center of the incident paced for hours, even appearing to smoke a cigarette at one point, but never made it past the federal courthouse’s security screening detectors.

In the final hour of the standoff, ABC7 cameras captured the man holding signs up to the window reading, “Help,” “Call Lawyer” and “No body cam?”

At one point, the man could be seen speaking on a mobile phone.

Throughout the afternoon, at least two FBI crisis negotiators were seen talking to the man.

“Some standoffs last for days, you know, and that’s why the FBI hostage negotiators are the best in the world,” Mayer said. “That’s what they do, because they do have patience, and they will take as long as it takes to make sure there is a positive outcome.”

FBI training materials for crisis negotiation reviewed by the I-Team give a detailed look at the agency’s tactics in an unpredictable situation like this, including a focus on active listening, empathy, building a rapport with a subject, then using that rapport to influence and effect behavioral change.

The FBI would not answer the I-Team’s questions about the suspect or standoff but in a written statement, Special Agent-in-Charge of the FBI Chicago Field Office Douglas DePodesta said, “I remain grateful that this situation resolved without incident, thanks to the heroic efforts of law enforcement professionals, and in particular, the U.S. Marshals Service and the FBI’s SWAT and Crisis Negotiations Teams.”

The person who caused the standoff was finally taken down by a horde of federal agents in tactical gear just before 8 p.m. on Tuesday.

The man was wheeled out of the courthouse on a stretcher, appearing alert and conscious, with a wound to his neck. He was taken to Northwestern Memorial Hospital in an ambulance in reportedly “good condition” as the investigation unfolds.

A 2008 Chevy Impala with a Nebraska license plate and busted-out driver’s side window broken was towed by investigators from the vicinity of the Dirksen. Nebraska officials told the I-Team the license plate was valid but, citing privacy laws, officials would not share any additional details on who the vehicle was registered to.

Mayer says investigators will be combing through the person’s social media, online communications, and what brought him to Chicago.

“Where did the suspect come from? Because if a suspect is willing to travel to somewhere else, other than where he resides, that’s something an investigator is going to want to know,” Mayer said. “Why did he travel to Chicago? Why did he pick this specific building?”

Mayer continued, “They’re going to do a deep dive into that.”