UPDATED 08/18/11 11:04 a.m.

CHICAGO (CBS) — A Southwest Side liquor store manager said Chicago Police officers beat him brutally after he complained about their mistaking him and his brother for robbers.

As CBS 2’s Susanna Song reports, Michael Ayala is manager of the 7-9-11 Liquor Store, at 4884 S. Archer Ave. He had broad bruises on both of his arms that he said were the direct result of what he calls a police beating.

“I never thought it would happen like that, where we would get brutally beaten,” Ayala said.

Ayala alleges 15 police officers turned on him and his brother as they were closing the store late Tuesday night.

“I was completely lost. The whole time, I was like, I didn’t know what was going on,” Ayala said. “I never expected this from Chicago Police.”

Ayala said before he and his brother left the store that night, he went back inside because he had forgotten his keys, but police mistook them for robbers.

“I come out, and they had my brother handcuffed. I come out, just telling them, ‘What’s going on? I’m the manager here,’” he said.

Ayala said he explained that he had the key and could disarm and re-arm the ADT security system to prove he was the manager of the store and not a robber, but the officers were not interested.

Ayala claims the officers interrogated him for half an hour.

“I told one of the cops, ‘I got you on camera, and I’m not going to let this go,” he said. “Now when that happened, the sergeant just flipped out on me and bashed my head right against this window right here.”

The store window to which he was referring was left cracked in a spider web pattern.

Ayala said he was also “bashed” all around his body by the officers.

After the beating, Ayala says he and his brother were arrested and taken to jail, as was his brother. They were released without charges soon afterward.

Ayala says he never did anything to provoke the beating.

“I never approached them to a point where I physically touched them,” he said. “I would never do that to an officer.”

A neighborhood watch sign warning that all suspicious activity will be reported to police is posted in the window of Ayala’s store. But he says in reality, he is now afraid of the police.

“I’ll probably take that off,” he said of the neighborhood watch sign. “I don’t think I’m going to be able to call the police, even if (criminals) rob the store.”

He said he has lost all trust in the police.

Ayala adds that he is working with the attorney and the owner of the store to get him a copy of the surveillance video. He says five cameras captured the beating.

Chicago Police responded to the allegations, saying, “The alleged conduct does not represent the high standards of professionalism and excellence maintained as core values of the Department, and which officers demonstrate on a daily basis serving and protecting the community.”

The Independent Police Review Authority is investigating the brutality allegations.

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