Thompson Square wins ACM vocal award in upset

The husband/wife duo comprised of Keifer and Shawna Thompson was surprised with the award onstage by ACM CEO Bob Romeo in front of thousands of fans at the ACM Salute to the Military Concert at the ACM Experience at Mandalay Bay in Las Vegas on Saturday night -- just moments after they had completed their set.

Thompson Square dethroned reigning Sugarland, who have won the award for two years. Love And Theft, Montgomery Gentry and Steel Magnolia also were nominated.

Thompson Square becomes only the third duo to win the ACM "Vocal Duo of the Year" Award in the past 20 years (since 1991) with Sugarland and Brooks & Dunn previously winning in the category respectively.

"It's been a long, long road," Keifer Thompson told the crowd. "This is one of the greatest nights of our lives." Overcome with emotion, he continued, "It's hard to talk when you're crying."

"This is a very bittersweet moment for me," added Shawna Thompson as she fought back tears. "More sweet than bitter. My dad passed away a month ago. This is for my dad."

The Thompsons pounded the pavement for 13 years in the music industry before finally signing to independent label Stoney Creek Records.

Thompson Square is currently criss-crossing the U.S. as part of Lady Antebellum's Own The Night World Tour.

Thompson Square will appear tonight as presenters on the show, which starts at 8 p.m. eastern on CBS.