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A police officer shot and critically wounded a man overnight in the restless suburbs of St. Louis, about a mile from where crowds gathered in a third night of unrest over the police killing of an unarmed black teenager.

Police in unincorporated St. Louis County said that the officer fired early Wednesday on a man who had turned and pointed a handgun at the officer. Police said they were responding to a report of four masked men with shotguns, and of shots fired.

In a separate encounter, a woman was shot in the head in an apparent drive-by shooting, authorities told NBC affiliate KSDK in St. Louis. Police said that her skull was not pierced and that she was alert and talking.

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It was not immediately clear whether either of those two shootings was related to protests that took place nearby on Tuesday night in an ongoing outcry over the killing of the unarmed teen, Michael Brown, in the suburb of Ferguson, Missouri.

Crowds chanting “No justice, no peace” poured out of a rally led by the Rev. Al Sharpton, squaring off against police and refusing orders to disperse or face arrest, KSDK reported. Tear gas filled the air for a third night.

KSDK described the protests as tense but mostly peaceful.

Details of what happened to Brown, 18, are hazy, but police have said that he was shot “more than just a couple of times.”

Brown’s family has pleaded for calm and demanded that police release the name of the officer who shot and killed the teen. The police chief had planned to release the name but backtracked on Tuesday, citing threats issued on social media sites.

Wow...A man picks up burning tear gas can and throws it back at police. #ferguson pic by @kodacohen @stltoday pic.twitter.com/SASXU1yF3E &- Lynden Steele (@manofsteele) August 13, 2014

The Federal Aviation Administration approved a no-fly zone over Ferguson, just north of St. Louis, after county police said that one of their helicopters had come under fire three or four times. The no-fly zone is expected to remain in effect until Monday.

The FBI has launched an investigation into Brown’s death, and President Barack Obama called Brown’s death “heartbreaking” while appealing for calm.

Vigils are planned across the country Thursday night in response to recent incidents of alleged police brutality, including Brown’s killing. Organized as part of the National Moment of Silence (#NMOS14), the vigils are set for 50 cities across 30 states.