After shots rang out, shocked fans scrambled to flee to safety as police worked to clear Union Station 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 incident, but the motive behind the shooting was still under investigation.
Kansas City fire department chief Ross Grundyson told a press conference that many of the victims had sustained “life-threatening injuries”.
Kansas City Chiefs beat 49ers to claim back-to-back Super Bowls, Mahomes MVP
Kansas City Chiefs beat 49ers to claim back-to-back Super Bowls, Mahomes MVP
A local radio station, KKFI, announced that one of its DJs, Lisa Lopez, had been killed in the assault.
“This senseless act has taken a beautiful person from her family and this KC Community,” the station posted on its Facebook page, referring to Kansas City.
A spokesman from Children’s Mercy said all those it was treating 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.”
Victims were treated lying on the ground before being carried away on stretchers as crowds streamed past.
“I am heartbroken over the tragedy that took place today,” Chiefs icon Travis Kelce wrote on X, formerly Twitter.
“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.
“Praying for Kansas City,” Chiefs quarterback Patrick Mahomes wrote on social media, while a statement from the team said they were “truly saddened by the senseless act of violence.”
Kansas City mayor Quinton Lucas was among VIPs at the event who were sent running for cover after shots rang out.
“This is a day that a lot of people look forward to. Something they remember for a lifetime. And what they shouldn’t have to remember is the threat of gun violence,” Lucas said.
US President Joe Biden echoed that sentiment as he 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”.
Just moments before the shooting, Kelce and his teammates had been soaking up the adulation from a sea of redshirted fans.
There had been no hint of trouble as hundreds of thousands of partying supporters feted Chiefs players along a 3km route in a procession of double-decker buses, enveloped by a blizzard of red and gold confetti.
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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.
Polls show a majority of Americans favour stricter gun regulations, but the powerful gun lobby and mobilised voters supporting the country’s culture of strong gun rights have repeatedly stymied lawmakers from taking action.
The Chiefs were celebrating their third Super Bowl title in five seasons after beating the San Francisco 49ers in overtime in Las Vegas on Sunday to cement the team’s dynasty status.
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.