The St. Louis Cardinals beat the Kansas City Royals 5-4 on Friday night at Busch Stadium, but the loudest reaction came from a patch of right field that filled with shirtless fans as the game stretched into extra innings. Yohel Pozo ended it in the bottom of the 11th with a pinch-hit line drive off a 100 mph fastball, giving St. Louis its fourth walk-off win of the season.

The scene started in the ninth inning, when the game was tied 3-3 and about 100 fans began moving to an empty section in right field. Caleb Cummings said he came up with the idea after telling a friend, “What if we go up there to right field bleachers and start waving our shirts?” Bryce Bradford was the first to take his shirt off and wave it around, and Cummings said the whole thing took off from there. “So then it just spread,” he said, adding that children, older fans and parents joined in as the section grew.

By the time the game reached extra innings, the right-field bleachers were packed. The St. Louis Post-Dispatch reported that the shirtless section kept growing as the night went on, turning what began as a small stunt into part of the ballpark atmosphere.

There was still baseball to settle. Cardinals pitcher Gordon Graceffo ended the top of the 11th by getting Kansas City’s Maikel Garcia to ground out, and Pozo followed in the bottom half with the winner. The finish matched the mood in the stands, where fans had spent the night pushing the game toward something louder than a routine win.

Manager Olli Marmol noticed. “Whoever started that in right field, I'll do whatever I need to do to make sure they come to every game,” he said. “Because that was awesome. Not only them, but everybody that showed up today. That was a fun environment.” For the Cardinals, the result was another walk-off. For the fans in right field, it was the kind of night Busch Stadium remembers long after the final out.