But the owner of the St. Louis bar that hosted the crowd said it was lightning - not wind - that killed the patron.
Seventeen were hospitalized and up to 100 people were treated at the scene after straight-line winds whipped through a large tent outside Kilroy's Sports Bar, near Busch Stadium. The crowd was celebrating after the Cardinals had beaten Milwaukee 7-3, a game that ended about 80 minutes earlier.
Eddie Roth, director of the St. Louis Department of Public Safety, said winds of about 50 mph shattered aluminum poles that held up the tent, located south of the stadium. The force of the wind Saturday afternoon blew the tent onto an adjacent railroad bridge.
Both Roth and Deputy Fire Chief John Altmann said they could not confirm a cause of death for the man killed. Roth said the man appeared to be in his 50s. His name was not immediately released.
"It was crazy, scary," said Annie Randall, whose family owns Kilroy's. "We're just so sorry this happened."
Janece Friederich was in the parking lot at Kilroy's when she saw dark clouds approaching. Before she could get out of the car and go into the bar, she saw the tent fly into the air.
"It looked like it just got ripped out because it ended up 100 feet in the air on top of the railroad tracks," Friederich said.
Kilroy's owner Art Randall described a short burst of a storm - perhaps five seconds, he said - with a massive wind that lifted the huge tent, threw it high into the air and sent the aluminum poles and most everything in the tent airborne.
When he heard the boom, he initially thought a train had derailed into the tent.
As the wind blew, a bolt of lightning crashed into the bar, Randall said. He said firefighters told him it was a lightning strike - not flying debris - that killed the man.
"At some point in that five seconds, we were getting lightning strikes, and apparently one of our customers got hit by lightning right in the middle of the dance floor," Randall said.
The bar owner said he screamed for help and three customers ran over to administer CPR, but they couldn't save the man.
Randall looked around "and saw 50 bodies scattered everywhere." He described a scene in which barstools, pedestals and a 100-pound bass amplifier were flying through the air. The disc jockey working the party was struck by the amp and knocked unconscious, he said, and people were scurrying to help one another.
"My wife had people in the beer cooler - we had the beer cooler loaded with injuries," Randall said. "It was a triage deal."
Most of the injuries were minor - cuts, bruises, twisted ankles, Altmann said. He did not have details about those with serious injuries.
Several bars and restaurants in the area around Busch Stadium set up tents throughout the baseball season to handle overflow crowds - Cardinals games are typically sellouts, or close to it. In addition to the baseball game, about 20,000 fans were downtown Saturday for a St. Louis Blues hockey playoff game.
Building Commissioner Frank Oswald said Kilroy's was granted a tent permit on April 11 and it passed inspection a couple of days later.
Oswald said the city requires tents to be able to withstand winds up to 90 mph, but he declined to speculate on whether Kilroy's could face discipline.
Both Oswald and Altmann cautioned that patrons need to understand that a tent is not a safe place to be in bad weather. St. Louis had been under thunderstorm watches and warnings for some time prior to the incident at Kilroy's.
"Tents are temporary structures," Oswald said. "They are certainly not designed in any stretch of the imagination to handle weather like this."
About two hours after the incident at Kilroy's, tornado sirens blared throughout the city after a funnel cloud sighting. There were several reports of tree damage, power lines down and damage from hail that in some parts of the region reportedly was as big as tennis balls. By late evening, about 2,600 Ameren UE electrical customers were without power in the city.