It was the Tweet heard 'round Austin.

Yet they weren't set to play the ACL Music Festival until the final night of Weekend Two, headliners The Killers took to the Twittersphere Thursday night to announce a secret show at midnight in downtown Austin.

The band tweeted the news from their verified account around 10:30 p.m.: "When in Texas, go BIG. @continentalATX 250cap. $20 a head, doors at midnight, 21+."

As many festival goers laid down their heads in preparation for the first day of Weekend Two, it didn't take long for dedicated fans to flock to The Continental Club on South Congress Avenue to snag a spot in line. After an hour passed since the band posted the official announcement on Twitter, the line had already stretched two blocks.

Though it wasn't all fun and games. As fans waited in anticipation for the clock to strike midnight, the fear set in and a sense of community wafted over the crowd. Would they make it to the doors in time before that 250-person capacity was hit? To make sure, anyone suspected of joining friends and cutting the line was quickly shut down by a huge unified "boo" from the crowd. The Killers fans don't mess around.

Once the doors were closed, the band kicked off with the first single, "The Man," from their new album, "Wonderful Wonderful." From that moment on, all tensions ceased as that feeling of "I got in!" resonated through the cramped house. People joined arms, raised their beers and rocked out in an intimate setting with The Killers -- only having to have paid $20 to see an ACL headliner.

Their secretive set featured over 10 songs, including other hits like "Mr. Brightside," "When You Were Young," and "Somebody Told Me."

Frontman Brandon Flowers also dedicated a special version of Tom Petty and the Heartbreakers' hit "American Girl," following Petty's recent death. He was 66.

This isn't the first time The Killers have slayed the headlines this week -- or in the last 24 hours even. The Killers also generated some buzz over an apparent private show on a downtown Austin rooftop only hours before their late-night set.

The Killers are slated to close out ACL on Sunday night.