One person was killed and children were among the 21 injured after a mass shooting at the Kansas City Chiefs’ Super Bowl victory rally on Wednesday triggered panic among huge crowds of fans.

Shots rang out moments after jubilant Chiefs players addressed a vast, cheering crowd, sending shocked fans and VIPs fleeing in a tragic end to what had been a joyous morning of celebrating the NFL champions.

Police said three people had been taken into custody after the attack near Kansas City’s Union Station, but the motive behind the shooting was still under investigation.

Fire department chief Ross Grundyson told a press conference that many of the victims had sustained “life-threatening injuries.”

A local DJ, Lisa Lopez, was killed in the assault, her radio station said. “This senseless act has taken a beautiful person from her family and this KC Community,” KKFI posted on its Facebook page, referring to Kansas City.

Children’s Mercy Hospital said it was treating 12 people — 11 of them children, nine for gunshot wounds — after the shooting. A hospital spokesman said all were expected to recover.

Paul Contreras, who was at the rally with his three daughters, said he tackled and disarmed one of the suspected shooters before the police arrived.

“I got the right angle on him and I hit him from behind. And when I hit him from behind, I either jarred the gun out of his hand or out of his sleeve,” Contreras said on CNN.

“I take him down, and I’m putting all my body weight on him. And then another good Samaritan comes over and is helping me,” Contreras said.

Victims were treated lying on the ground before being carried away on stretchers amid the commotion and the crowds, while the hundreds of police guarding the event rushed to clear the area.

Chiefs star Travis Kelce said he was “heartbroken”.

“My heart is with all who came out to celebrate with us and have been affected. KC, you mean the world to me,” he wrote on X, formerly Twitter.

“Praying for Kansas City,” quarterback Patrick Mahomes wrote on social media, while a statement from the team said they were “truly saddened by the senseless act of violence.”

US President Joe Biden issued a rallying call for Americans to back his pleas for Congress to enact gun reform, saying Wednesday’s shooting “cuts deep”.

“Today’s events should move us, shock us, shame us into acting,” Biden said in a White House statement.

He called on Americans to “make your voice heard in Congress so we finally act to ban assault weapons, to limit high-capacity magazines, strengthen background checks, keep guns out of the hands of those who have no business owning them or handling them.”

‘So depressingly American’

Just moments before the shooting, Kelce and his teammates had been soaking up the adulation from a sea of red-shirted fans.

There had been no hint of trouble as hundreds of thousands of partying supporters feted Chiefs players along a three-kilometre route in a procession of double-decker buses, enveloped by a blizzard of red and gold confetti.

Local officials said more than one million people were expected for the parade, which was held in unseasonably sunny, warm conditions in downtown Kansas City.

Mass shootings are common in the United States, where there are more guns than people and about a third of adults own a firearm.

The attack in Kansas City wasn’t even the only shooting to grab national headlines Wednesday: four students were also shot outside an Atlanta high school, while three police officers were shot during a standoff in the capital Washington. All are expected to survive, according to media reports.

The shootings came six years to the day after 17 people were killed in an attack at a high school in Parkland, Florida.

“There is something so depressingly American about experiencing a mass shooting at a Super Bowl celebration on the anniversary of another mass shooting,” posted March For Our Lives, a student-led advocacy group seeking gun control that formed after that shooting in Parkland, a suburb of Miami.

Polls show a majority of Americans favour stricter gun regulations, the powerful firearms lobby and mobilized voters supporting the country’s culture of strong gun rights have repeatedly stymied lawmakers from acting.

The Chiefs were celebrating their third Super Bowl title in five seasons after beating the San Francisco 49ers in Las Vegas on Sunday.

The team’s most famous fan — music superstar Taylor Swift, whose relationship with beau Kelce has become a cultural phenomenon — was not part of the celebrations.

She was reportedly en route to Australia, where she is due to perform in Melbourne on Friday.