Updated

An undercover St. Louis police officer and an Air Force lieutenant who lives in the neighborhood were among several people who say they were forcibly arrested last weekend even though they were not participating in protests over the acquittal of a white former officer in the killing of a black suspect.

About 120 people were arrested — most for failing to disperse — about two hours after vandals broke some windows and threw items at officers last Sunday. The officers used a tactic called kettling that boxed in demonstrators and others in the area.

The city's acting police chief and Gov. Eric Greitens praised the officers for controlling the demonstrations, but there has been growing criticism of their actions as details have emerged. The American Civil Liberties Union filed a lawsuit Friday alleging that the police violated people's civil rights, and two top city officials have said some police actions were "disturbing."

Police said people were arrested only if they didn't follow orders to disperse, but some people said they had nowhere to go because police had boxed them in.

The undercover officer was mistaken for a suspect who was carrying chemicals that could be sprayed on officers. When the man refused to show his hands, he was knocked down and hit several times, with his hands tied behind his back and his mouth was bloodied, The St. Louis Post-Dispatch reported .

On Friday, Mayor Lyda Krewson asked the director of public safety to investigate how the officer was treated.

During the same protest, Air Force Lt. Alex Nelson, 27, who lives in the neighborhood with his wife, said they were trapped in the kettling, the tactic police used to box in demonstrators. He said he was kicked in the face, blinded by pepper spray and dragged away.

"I hear the police say it was their street, but it's literally my street," he said. "I have coffee on that street, and I own property on that street. We were not active protesters. We were looking into the neighborhood to observe events that were unfolding."

He said the police actions were "incredibly unnecessary" because he followed every demand and officers never gave an order to disperse. He said when he told an officer he was with the military, the police officer replied, "Shut up. Stop. I don't care."

A documentary filmmaker from Kansas City who was visiting with his wife said he was knocked unconscious during the sweep. Drew Burbridge, 32, said he never heard orders to disperse until officers started to advance, banging their batons and chanting, "Move back."

"I turned my camera off and asked if there was anywhere I could go, but I was denied the right to leave," he said. "I didn't want to be a part of this."

He said after he was on the ground, officers grabbed him by both arms and dragged him away. He said he was sprayed with a chemical and eventually knocked unconscious for 10 to 30 seconds and when he came to, an officer pepper sprayed him again.

More than 160 people have been arrested since demonstrations began Sept. 15 after a judge found Jason Stockley not guilty of first-degree murder in the 2011 death of Anthony Lamar Smith. Most of those arrests were on the night of the ruling and last Sunday.

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Information from: St. Louis Post-Dispatch, http://www.stltoday.com