Investigators in Kansas City, Mo., were seeking help from the public as they searched on Thursday for answers in a shooting that upended the city’s Super Bowl victory celebration and left one person dead and at least 21 others wounded by gunfire.

The shooting, which erupted on Wednesday afternoon as thousands of football fans had crowded into downtown Kansas City, sharply turned a day of revelry into one of chaos and confusion. As shots rang out, people ran for cover.

Among the wounded: 11 children, ages 6 to 15. Nine of them had suffered gunshot wounds, the authorities said.

It was uncertain who was responsible for the shooting, which took place near the city’s Union Station, a hub that draws tourists to the city each year. By Wednesday night, three people had been detained, the Kansas City police chief said, but no charges had been announced, and officials said they were uncertain of the motive.

The police were trying to determine whether one of the three in custody had been tackled by fans at the rally, referring to videos circulating online, and they requested help from anyone in the public who had been at the celebration and had videos.

The police chief, Stacey Graves, said the authorities were still working to identify the deceased victim and notify the person’s family.