Skrillex and Diplo perform as Jack U during the Ultra Music Festival at Bayfront Park Amphitheater on March 30, 2014 in Miami
Tim Mosenfelder/Getty Images

Update (9/22): Diplo says the stabbings occurred during David Guetta's set, not Jack Ü's.

Original story (9/21): Skrillex and Diplo teamed up this year to give us great joy in the guise of Jack Ü, that EDM superduo behind the Justin Bieber collaboration "Where Are Ü Now." (Don't confuse it with the Biebs' history-making chart-topper/career revitalizer "What Do You Mean?")

But a recent Jack Ü show ended in horror for some attendees. TMZ has discovered that a Labor Day weekend performance in Las Vegas saw four people "seriously stabbed" when "a huge fight involving around 20 people broke out in the middle of the show." Officials arrested a suspect now facing three charges of attempted murder.

"We're told the injuries were serious including a punctured lung and spleen," TMZ writes, "but everyone survived—one victim admitted to gang ties and didn't want to go forward with any charges."

In less grim news, Skrillex was joined onstage by Babymetal in Japan over the weekend.