A car drove through a Christmas parade in Waukesha, Wisconsin, on Sunday afternoon, leaving several people dead and more than 20 injured, including children, authorities said.

Dozens of emergency officials responded after the incident around 4:40 p.m. local time. A livestream video of the event appears to show a red SUV speeding through the parade route, troubling those gathered on the street. A police vehicle is seen rushing through the crowd soon afterward before the attendees begin to disperse.

The city’s police chief, Dan Thompson, said authorities have identified one person of interest who is in custody, although he added that officers were still probing a “very fluid investigation.” The chief added that the scene was safe and there were no further threats to the public.

At least 11 adults and 12 children were transported to six area hospitals after the incident. Officials would not provide any further details about the number of fatalities or the ages of those who died.

“Tonight was a traumatic situation for the city of Waukesha,” the city’s mayor, Shawn Reilly, said. “We don’t have all the details. We can’t provide details at this point.”

Those on the scene described a festive atmosphere that quickly turned tragic after the car careened through safety barricades set up along the city’s Main Street.

“As we were walking back in between the buildings that we saw an SUV crossover, just put the pedal to the metal and just zooming full speed along the parade route,” Angelito Tenorio, an alderman for West Allis, Wisconsin, told the Milwaukee Journal Sentinel. “And then we heard a loud bang, and just deafening cries and screams from people who are struck by the vehicle.”

He said he saw people running from the scene crying, and people on the ground who appeared to have been hit by the car.

Local reporters said it appeared that multiple people were on the ground shortly after the incident. Thompson said an officer discharged his weapon at the suspect’s vehicle, but there was no more evidence so far of any other gunfire.

Many families were at the event with young children.

Corey Montiho, a member of the Waukesha School Board, told the Journal Sentinel his daughter’s dance team was marching in the parade and many members were hit by the SUV.

“They were pom-poms and shoes and spilled hot chocolate everywhere. I had to go from one crumpled body to the other to find my daughter,” he told the paper’s Molly Beck. “My wife and two daughters were almost hit.”

The Milwaukee Dancing Grannies, a self-described “group of grannies” that marches in about 25 parades a year, said members of their group were participating in Sunday’s event and impacted by the vehicle, but didn’t have any more information.

Gov. Tony Evers (D) called the incident a “senseless act” and said his office was awaiting more information.

Kaylee Staral, an intern at the Milwaukee Journal Sentinel, was at the parade on Sunday. She told CNN the SUV came “running down the middle of the street” and hit “a lot of people.”

“After the SUV left, there were multiple people on the ground, and the police came through a little later saying at least 30 on the ground,” Staral said. She added that the car was going “very fast.”

The Waukesha Christmas Parade, held about 17 miles west of downtown Milwaukee, is an annual event that has been held for more than 50 years. The city describes it as a holiday tradition that brings together “local civic groups, business, schools, public services and entertainers each year on the Sunday before Thanksgiving.”

Photos posted on the city’s Instagram account showed many people sitting on the curb just off the parade route.

The theme this year was “comfort and joy.”

Wisconsin has been on edge for days following the trial of Kyle Rittenhouse, who on Friday was found not guilty after killing two people during a Black Lives Matter demonstration last summer. Protests following the verdict have been largely peaceful in Kenosha, Wisconsin, where the trial was held.