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Waukesha, Wisconsin, authorities say a driver slammed into almost two dozen people, half of them children, at the community’s Christmas parade Sunday evening.

Police confirmed multiple fatalities and said many people were injured. Waukesha Police Chief Daniel Thompson said at an 8 p.m. CT news conference that more than 20 people were struck – an undisclosed number of them fatally. Authorities did not release the victims’ names but said there were 11 adults and 12 children.

"Some of the victims were children, and there were some fatalities in relation to this incident," he said, adding that police were still in the process of notifying victims’ families.

Good Samaritans attempt to help victims after an SUV plowed through the Waukesha Christmas parade Sunday evening in Waukesha, Wisconsin. (Credit: @J_Woynilko)

Good Samaritans attempt to help victims after an SUV plowed through the Waukesha Christmas parade Sunday evening in Waukesha, Wisconsin. (Credit: @J_Woynilko) (@J_Woynilko)

SUV PLOWS THROUGH WISCONSIN CHRISTMAS PARADE

An officer opened fire on the fleeing vehicle, the chief said, and they later took a person of interest into custody.

Eyewitnesses described a blood-soaked stretch of road with good Samaritans attempting CPR on victims – who had been thrown across the asphalt when a speeding driver plowed through a barricade and then pedestrians.

Jordan Woynilko, a Milwaukee man who shared video of the incident’s aftermath under his Twitter handle, @J_Woynilko, told Fox News digital Sunday evening the red SUV that slammed into participants Sunday struck almost two dozen people as he was stepping out of a pub along the parade route.

(@J_Woynilko)

"As I was opening the door to walk out, people started yelling and running in -- and that's when I saw the red SUV," Woynilko said. "I saw it drive through and hit the people."

WAUKESHA CHRISTMAS PARADE: 5 DEAD, 40 INJURED AFTER SUV PLOWS THROUGH WISCONSIN CROWD: LIVE UPDATES

He said he grabbed his friend, and they were both in shock as they made their way through the carnage. Good Samaritans were attempting CPR on multiple victims before paramedics arrived, he said.

(@J_Woynilko)

"There were moms and dads yelling for their kids, people running around," he said. "When I rewatched the video, I could hear people talking, and they were like, 'There's eight people injured down there. We need an ambulance over here.' There's one lady kneeling on the ground crying."

Brayden Kowalski, a 19-year-old man who grew up in Waukesha, said that he was at the parade with his family when he saw an SUV accelerate through the crowd. 

"He’s just blowing through people, kind of just dinging a lot of people, bodies flying everywhere," Kowalski said. "These people didn’t get run over, they got f------ thrown through the air. Like a lot of people got tossed up into the air."

Almost immediately after the SUV went through the crowd, Kowalski and his mom went out into the crowd to try to help people who were hurt. "You could see the fragments of brains," he said. "There were quite a few people with broken limbs, like a lot of broken legs, a lot of people shouting with broken legs. It was horrifying."

Moments before the chaos, Woynilko said children along the route had rushed up to the edge of the parade, where they received candy.

"This was 100% intentional in my opinion," he said. "He drove through the barriers on purpose, broke them, and he hit multiple people. If it was an accident, I could see that happening and maybe him stopping or driving off after hitting one person – but I saw at least 10 people laying on the ground. That was definitely intentional."

(@SamKraemerTV/Fox6)

Woynilko said that as he rushed his friend to safety and left the area, he overhead police officers describing the suspect as a Black male either in the red SUV or on foot.

Federal authorities are also assisting local police. An ATF spokesperson told Fox News Digital that the bureau sent special agents from its Milwaukee field offices to aid Waukesha investigators, and the FBI said local and state authorities were leading the response.

Waukesha County Executive Paul Farrow wrote in Twitter that the SUV careened into the crowd shortly after he and his wife wrapped up their participation in the parade.

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"This is an unspeakable tragedy, affecting us all as we work to overcome an extremely challenging two years and resume our cherished holiday traditions," he said. "Keep the families affected in your thoughts as we work to offer whatever support we can."

The incident comes just days after a jury in nearby Kenosha found Kyle Rittenhouse not guilty of homicide and other charges after he successfully argued self-defense after shooting three protesters who attacked him at a violent demonstration last summer, two of them fatally.

Although the victims were all White, the case stoked racial tensions as critics leveled unsubstantiated claims against the teen defendant painting him as a White supremacist.