CHICAGO (CBS) — Chicago Police Supt. Garry McCarthy said Monday it was just a miscommunication this weekend, when police officers at Sunday’s anti-NATO demonstration began putting on their gas masks.

“I think what occurred was, there was a description of someone in the crowd wearing a gas mask,” he said.

McCarthy says the word “mask” got repeated several times, and officers thought it was an order.

LISTEN: WBBM Newsradio’s Brandis Friedman reports

“I gotta tell ya, when I turned around and saw everybody kneeling down and putting on gas masks I said, ‘Wait a second, I’m supposed to give the order for gas,'” McCarthy explained. “Then I thought, ‘Maybe they’re going to be throwing gas at us.'”

Police were able to determine there was no threat, and officials gave the all-clear.

“That was just a miscommunication,” McCarthy said.

The superintendent said morale among his officers is good, and he couldn’t be more proud of them.

He explained eight officers were injured during Sunday’s protest march and rally, including one hospitalized for exhaustion. Another officer was stabbed in the leg, but McCarthy said that officer was back at work helping other officers hold the line on Michigan Avenue Sunday night.

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