Chicago Police Superintendent Eddie Johnson appeared before reporters during a press conference to explain the incident.
He said that this afternoon there was a report of a suspicious person spotted by a police officer who was patrolling the grounds by the Thompson Center, otherwise referred to as the State of Illinois Building, which is fit with businesses on the first floor and a food court on the floor below.
An officer made the initial contact with the suspect but the person fled. Then Cmdr. Paul Bauer, a decorated officer, spotted the suspect and engaged him but was shot multiple times, Johnson said.
Responding officers managed to arrest the suspect, according to Johnson. A weapon was recovered at the scene.
Bauer was rushed to Northwestern Hospital, where he was pronounced dead.
Johnson, who broke into tears while describing the incident, said that Bauer is survived by his wife and daughter.
Bauer’s body was led out of Northwestern Hospital by a convoy of mourning cops to the medical examiner’s office.
Already, there has been a flood of support for the fallen commander.
Gov. Bruce Rauner initially offered thoughts and prayers to “the family and colleagues of the officer tragically lost in a shooting at the Thompson Center today.”
Then the governor honored Bauer by name.
Chicago Mayor Rahm Emmanuel also extended his condolences.
In a tweet, the mayor asked “every Chicagoan” to keep Bauer’s family “in their thoughts and prayers.”
ABC News’ Rachel Katz contributed to this report.