The gunman who killed Bauer was carrying a semi-automatic handgun that contained an extended clip of ammunition, a police official told The Associated Press. The man ran from the "Central District tactical officers" who gave chase.
Cmdr. Paul Bauer was shot Tuesday after spotting a man matching the radio description of an armed suspect.
"The idea that Paul would act so unselfishly and would sacrifice his own safety for the safety of the people of Chicago and his fellow officers comes as no surprise to those of us who knew him", the statement read.
Thought and prayers to the family of Commander Bauer.
"Even when we catch somebody", said Bauer, "there's still a long way to go to get them off the street".
Bauer leaves behind a wife and a 13-year-old daughter.
And Father Michael Pfleger, who may have been at odds with Bauer at times over gun violence in Chicago, recalled the commander as "always a gentleman and professional", but said his death is but another tragedy for Chicago.
Commander Bauer was known for advocacy for tougher sentences and harsher policing tactics against career criminals like the man now held for his slaying.
"This is like a gut-punch to the police department".
Mayor Rahm Emanuel was preparing to board a flight in Los Angeles to head home Tuesday afternoon when he was told of the shooting.More news: Trump responds to article on USA intel operation: 'Drain the swamp'
Two women who work at a bank in the Thompson Center said they heard shots and later saw a person being wheeled away on a stretcher with a sheet over him.
"He observed the offender", Johnson said.
The mayor also delivered flowers to Bauer's family home in Bridgeport on Wednesday.
Johnson choked back tears as he spoke to reporters outside Northwestern Memorial Hospital, where Bauer was pronounced dead.
Authorities at the scene of Tuesday's fatal shooting of a police commander..
Detectives have been working through the night combing through evidence and building a case against the suspect.
Chicago Police scheduled a news conference for after 4:15 p.m. Wednesday to announce charges.
Bauer had recently criticized Chicago's justice system for what he saw as excessive lenience in prosecuting and jailing career criminals. Guglielmi said detectives have been combing through a vast amount of video evidence from various cameras downtown, including police surveillance cameras, taxi cameras, social media posts, and cell phone videos from witnesses.
"Thank You CPD" signs adorned nearby windows, and flowers marked the spot of Bauer's death.