"You think a lot of things after that, you know. He could have tried to get somebody else car and try to run away," said the man, who wished to remain anonymous.
It began with a traffic stop Thursday on Cicero Avenue near the Stevenson Expressway, according to police.
"The vehicle refused to stop. Our officers were able to box the vehicle in," said Cicero Police Superintendent Jerry Chlada. "The subject immediately exited his vehicle and began shooting multiple rounds at our officers."
Cicero Police officer Luis Duarte was shot multiple times. Police said the suspect continued shooting at Duarte's partner as he ran.
That's when the 42-year-old concealed carry permit holder jumped out of his red Jeep.
"I fired my arm three times to try to stop the suspect," he said.
It's unclear whether he or an officer wounded the suspect, who was arrested and taken to a hospital.
The man said he then applied a towel to Duarte's wounded shoulder as the 4-year veteran called for help.
"I don't regret it. It's what happened," the man said. "I tried to help. I do my best."
The 31-year-old officer remains hospitalized in in good condition. Officials said he had to undergo some surgery, but is doing very well.
Chicago police and the Illinois State Police all assisted with the response and now are taking over part of the investigation.
"Chicago police are handling the criminal aspect of these investigation. Illinois State Police Public Integrity Task Force is handling the officer involved shooting," said Chicago Police Department Sgt. Rocco Alioto.
The Chicago Police Department is handling the criminal investigation, and the Illinois State Police Public Integrity Office will handle the officer-involved shooting aspect of the incident.