Simon Cowell left speechless and Howie Mandel choked up by “America's Got Talent ”performance: 'You just broke us'

Twelve showstopping acts performed in the semifinals.

Veteran TV judge Simon Cowell usually always has something to say when judging reality competitions such as American Idol, The X Factor, or America's Got Talent. But that wasn't the case on Wednesday's AGT semifinals.

After drone act Sky Elements finished an oudoor performance dedicated to member Preston Ward's late infant daughter, Briley Rose, Cowell was left speechless. (Watch the moment he was overcome with emotion about 3:15 into the video below.)

"That was, uh, that was, um — oh gosh," Cowell said as he searched for words and gave up.

Sky Elements was the act that prompted him to break the show's rules in the auditions round and grant each judge an additional Golden Buzzer to protect their favorite acts.

Related: Simon Cowell says he didn't give group 'credit they deserved' on America’s Got Talent

From the other end of the judges' table, Howie Mandel noted that the loving tribute, which featured a giant rose and butterflies, was a fitting one to air on Sept. 11, when so many people lost loved ones.

"I can't thank you enough for this," Mandel told Sky Elements. "And I'm looking at your family members... There isn't an act that just moves your heart this much, and you just broke us."

The other two judges, Sofia Vergara and Heidi Klum, were just as affected.

Related: America's Got Talent's Sofía Vergara gives 'difficult, dangerous' act first-ever direct pass to the finals

"I mean, who knew that drones could make you so emotional?" Vergara asked. "That was a surprise. That was so beautiful! That was, like, heartfelt, and I mean, I don't even know what to say. Congratulations! What a beautiful, beautiful job."

Meanwhile, Klum said, "I just want to give you a big hug right now."

Earlier in the show, Kelsey Jane, the aerialist who happens to be a dentist in her offstage life, told Cowell that, even if she wins the show's $1 million prize, she plans to keep practicing. School janitor and singer Richard Godall wowed with his rendition of Survivor's Rocky song "Eye of the Tiger," and Roni Sagi and her dog Rhythm delighted with their dancing. Quick-change artist Solange Kardinaly, magician Young Min, and Young singers Alex Sampson, Ashes & Arrows, Pranysqa Mishra, and Reid Wilson were at the top of their game. Comedian Learnmore Jonasi and dance group Brent Street made their cases too.

The night featured 12 impressive acts in all vying for six spots in the final round of performances. The six acts that receive the most votes from the public will be revealed on the Sept. 12 results episode. From there, those six, as well as the four acts who received the Live Show Golden Buzzer, will form the group of 10 finalists. They will perform one more time, on Tuesday, Sept. 17, and one will be named the winner on the Sept. 24 finale.

But first, results of the semifinals will be revealed on the America's Got Talent live results show on Thursday, Sept. 12 at 8 p.m. on NBC.

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