Sylville Smith was fatally shot Saturday, kicking off a wave of protests in the city.
A wave of protests moved across Milwaukee over the weekend after police there shot and killed an armed black man.
One person was shot Sunday in the second night of protests after police gunned down 23-year-old Sylville Smith the day before.
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It was a calmer night than Saturday, when multiple businesses burned to the ground and 17 were arrested.
In a press conference late Monday morning, the Milwaukee Chief of Police said there were "many shots fired" on Sunday and 14 were arrested.
Two dozen officers in riot gear confronted over 100 protesters who were throwing rocks and other objects at police near where Smith was killed.
The man shot Sunday was 18, police said. Milwaukee County Sheriff's Office officials said they continue to search for suspects.
At a press conference early Sunday, Milwaukee Police Chief Ed Flynn said Smith turned toward an officer while holding a gun and began to raise the weapon despite orders to put it down.
While autopsy results are pending, Flynn said the officer "certainly appeared to be within lawful bounds" based on body camera video.
Flynn also said the officer is black.
Mayor Tom Barrett spoke at the news conference and stressed the danger posed to the officer who opened fire. "I want our community to know that" Smith had a gun, the mayor said.
Gov. Scott Walker put Wisconsin's National Guard on standby Sunday with 125 Guard members at the ready for potential deployment.
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"Following a request from Milwaukee County Sheriff David Clarke, and after discussions with Milwaukee Mayor Tom Barrett and Adjutant General Donald Dunbar, I have activated the Wisconsin National Guard to be in a position to aid local law enforcement upon request," the presidential also-ran said in a statement.
While defending his decision to bring in the National Guard, the outspoken Sheriff Clarke appealed to the city to "fix the ghetto."
"We cannot have a repeat of what happened Saturday night. Stop trying to fix the police, fix the ghetto. We have a growth of the underclass here in Milwaukee. And we saw some of their behaviors on display..." he said. "Fortunately, the loss of life of innocent civilians and law enforcement personnel did not happen. I think only by the grace of God, with bullets flying all over the place."