Who Is Jason Aldean? Country Music Superstar Who Performed at Fatal Route 91 Festival Says Las Vegas Shooting 'Beyond Horrific'

Country superstar Jason Aldean was just 20 minutes into his headline performance at Route 91 Harvest Festival in Las Vegas Sunday night when a lone gunman opened fire in what is now being considered the deadliest mass shooting in U.S. history.

At least 50 people were killed and 200 injured after suspected gunman Stephen Paddock began his assault on the music event at the Mandalay Bay Resort and Hotel at around 10.30 p.m. local time.

But who is Aldean, the singer who was performing onstage when the shooting happened?

Who is Jason Aldean?

Aldean, 40, is a country musician who shot to fame in 2005 with the release of his self-titled debut album. He has released seven studio albums in total, including 2010's My Kinda Party, his most successful album that was certified four-times platinum by the Recording Industry Association of America (RIAA).

Aldean—the main headliner for the three-day country festival—has amassed 19 number one singles on the U.S. Hot Country Songs and Country Airplay charts.

His big hits include "Dirt Road," "She's Country" and "Burnin' It Down."

The singer has also had some extremely popular collaborations, including "Don't You Wanna Stay," a duet with pop singer Kelly Clarkson, and "The Only Way I Know," which featured fellow country music heavyweights Luke Bryan and Eric Church.

How did Aldean respond to Sunday's attack?

The Grammy-nominated singer had only been on stage for 20 minutes when suspected shooter Paddock began his assault on an audience of around 40,000 country music fans.

Aldean quickly stopped his performance as the first shots rang through the open-air venue and evacuated the stage.

In the early hours of Monday morning, he posted his first official statement about the events on Instagram.

"Tonight has been beyond horrific," Aldean captioned an image of Las Vegas with the words "Pray for Las Vegas" emblazoned on it.

"I still don't know what to say but wanted to let everyone know that me and my crew are safe. My thoughts and prayers go out to everyone involved tonight. It hurts my heart that this would happen to anyone who was just coming out to enjoy what should have been a fun night. #heartbroken #stopthehate"