Three people were in custody in Kansas City, Missouri, on Thursday, facing questions about what led to a deadly mass shooting near the city's Super Bowl victory rally and who was behind it.

At least one person was killed and 21 others wounded by gunfire on Wednesday outside the city's landmark Union Station, where thousands of fans had gathered with the Kansas City Chiefs to celebrate the team's NFL championship triumph over the San Francisco 49ers, authorities said.

The bloodshed, which came at the end of the rally following a parade, turned the festive occasion into a scene of panic as throngs of attendees scrambled for cover at the sound of rapid-fire gunshots.

Local radio station KKFI identified the slain victim as Lisa Lopez, one of its disc jockeys and host of the show "Taste of Tejano." Fifteen other victims suffered life-threatening wounds, Fire Department Chief Ross Grundyson said at a late-afternoon news conference.

Eleven of those hurt by gunfire or the ensuing pandemonium were children as young as 6, officials said.

None of the football team, their coaches or other staff attending the rally was injured, the team said.

Police Chief Stacey Graves told a Wednesday evening news conference three people were detained "and under investigation" in connection with the shooting, but she said investigators had yet to determine a motive.

CIRCUMSTANCES REMAIN MURKY

She said police were still unsure whether the Super Bowl victory celebration was targeted for attack, or whether the violence was incidental to the event and spilled over into it.

Authorities appealed to anyone who had information about the shooting or video that might help shed light on what transpired to share it with police.

Graves said she was aware of video purporting to show fans subduing a suspect, and that investigators were reviewing the footage to determine if the individual was one of the people taken into police custody.

Parade attendee Paul Contreras, told local television station KETV he was one of the fans who helped tackle the man, and saw him drop a gun when he was knocked down.

"The whole time he's fighting to get up and run away," Paul said, adding police arrived within moments. "We're fighting each other, you know. We're fighting to keep him down and he's fighting to get up."

Kansas City Mayor Quinton Lucas lamented that city authorities ultimately were unable to prevent such violence despite the presence of more than 800 law enforcement officers, including federal agents, on security detail for the event.

"Parades, rallies, schools, movies - it seems like almost nothing is safe," Quinton, a Democrat, told reporters, recounting how he was among those who ran for cover at the sound of gunfire.

The barrage of gunshots happened near a garage west of the station, whose front entrance was the backdrop to the stage for the victory rally, according to police and local media.

Union Station, a 109-year-old Beaux Arts building that once served as a major U.S. rail hub for passenger and freight traffic, is home to a museum and visiting attractions today, and is a terminal for Amtrak passenger service.

The Super Bowl celebration featured Chiefs tight end Travis Kelce on stage with quarterback Patrick Mahomes and other teammates, but Kelce's pop superstar girlfriend, Taylor Swift, was back on tour in Australia at the time.

The governors of Missouri and Kansas were among the dignitaries present at the event but they, too, were unhurt.

The shooting came three days after the Chiefs defeated the 49ers in overtime to win the Super Bowl, 25-22, marking their fourth National Football League championship.

On June 17, 1933, Union Station was the site of an outdoor shootout and murder of four law enforcement officers and a criminal fugitive in a notorious incident known as the Kansas City Massacre.

Wednesday's violence took place on the sixth anniversary of one of the most notorious mass shootings in recent US history, when 17 people were killed and 17 more were injured at Marjory Stoneman Douglas High School in Parkland, Florida. The shooter in that incident, a former student who was 19 at the time, pleaded guilty and was sentenced to life in prison.