Tom Lashinski was walking his mother's small dog in the North Center neighborhood early Sunday when he noticed two people scuffling in an alley.
"It was like something out of Batman ... with Batman jumping into someone and people rolling around and getting up and going back at it."
The Belmont District officer -- assigned to watch over Mayor Rahm Emanuel's home nearby -- was straddling the suspect, her arms locked on to his.
Spotting Lashinski, who had a cell phone in his hand, the officer yelled for him to call 911. She also asked him to grab her police radio to signal that an officer was in danger.
"I had to reach and get the radio for her, the guy was struggling and kicking, and I had to stand on his legs," said Lashinski, 28.
Within minutes, 10 to 15 police vehicles arrived.
Police said the incident began around 12:30 a.m. in the 4200 block of North Ravenswood Avenue began when the officer spotted a man breaking into a car near Emanuel's home, according to Chicago Police News Affairs Officer Michael Sullivan.
The suspect -- identified as Anthony Perez, 45 -- began biting, punching and kicking the officer and tried several times to pull the officer's gun from her holster, Sullivan said.
By the time Lashinski came to her aid, the officer had bloody gashes on her arms. The man had lost a tooth, he said.
"He was struggling for all his worth," Lashinski said. "It was a very intense thing. I'm just glad I got there when I did. You can't hold someone like that forever."
Police are calling him a Good Samaritan who stepped up when an officer needed help.
But Lashinski downplayed his role. "Anyone who attacks a police officer must be pretty desperate," he said. "I'm just glad she's OK."
The officer was treated at Advocate Illinois Masonic Medical Center and released.
Perez, of the 4200 block of North Kenmore Avenue, is a convicted felon with more than 30 arrests. He was charged with aggravated battery to a police officer, burglary, resisting arrest and attempting to disarm a police officer. He is expected to be in bond court on Monday.
Man comes to aid of struggling cop: 'It was like something out of Batman'
Anthony Perez (Police photo)