Watch the teen's unusual performance of Otis Redding's 'Hard to Handle,' which wowed Simon Cowell and Howie Mandel

When shy 13-year-old Courtney Hadwin stepped onto the America’s Got Talent stage Tuesday night, no one saw her performance coming.

After admitting she was “a little bit nervous” as she awkwardly answered Mel B‘s pre-performance questions, Hadwin began belting Otis Redding’s “Hard to Handle,” dominating the stage as she fearlessly played to the judges and packed crowd.

Heidi Klum‘s jaw hit the floor as she said, “Oh. My. God,” in the middle of the performance. And her fellow judges followed suit.

America's Got Talent - Season 13
Credit: Ron Batzdorff/NBC

“Bloody hell, Courtney,” Simon Cowell said. “You were like this shy little thing when you first came out, and then you sing. You’re like a lion.”

Howie Mandel compared the British teen to a music legend before hitting the coveted Golden Buzzer that sends her straight through to the live shows later in the season.

“You are not from this era. You’re from a whole different era. And I’m a huge Janis Joplin fan and there’s a story — if you’ve ever watched the documentary — Clive Davis, he goes to the Monterey Pop Festival and he sees this young girl that nobody’s ever seen before, that nobody knows. It was the first time that Janis Joplin got signed and that changed her life. I’m not Clive Davis, I’m Howie Mandel, and I can’t sign you to a record deal. The only thing I can do for you, young lady, is give you…”

Mandel then slammed his hand on that buzzer as confetti began to fly and Hadwin burst into tears.

“I didn’t know what to expect when I auditioned for @AGT but the golden buzzer was more than I ever could have dreamed of,” Hadwin, who was a finalist on The Voice Kids U.K., wrote on Twitter. “Thank you so much @howiemandel I am so happy and can’t thank you enough xx”

America’s Got Talent airs Tuesdays at 8 p.m. on NBC.