A shooting near Union Station in Kansas City, Mo., on Wednesday afternoon left one person dead and at least 21 others with gunshot wounds, including nine children.

The eruption of violence came as thousands of people had gathered for a public celebration of the Kansas City Chiefs’ Super Bowl win, and transformed a day of joy and civic pride into one of loss and fear.

Here is what we know about the shooting so far:

It was unclear who was responsible for the shooting.

Three people had been detained, Chief Stacey Graves of the Kansas City police said, but she did not name them. Investigators had not identified a motive, she added, and were working to tally the number of rounds that had been fired.

The chief asked the public to provide any video or other information that could help the authorities determine what had happened.

Chief Graves said Wednesday that the authorities were still working to identify the deceased victim and notify the person’s family.

Medical centers in the area took in more than two dozen patients, hospital officials said.

Children’s Mercy Hospital said it was treating 11 children, ages 6 to 15, and one mother who would not leave her child during the shooting. Nine of the children suffered gunshot wounds. None of the children were in critical condition, and all were expected to recover.