Route 91 Harvest Festival: What Is the Country Music Concert Under Siege in Las Vegas Shooting?

People carry a wounded person at the Route 91 Harvest country music festival in Las Vegas after gunfire was heard, on October 1. (Photo by David Becker/Getty Images)

A gunman who opened fire on revelers late Sunday night outside the Mandalay Bay Resort and Casino targeted the last night of a three-day-long country music event, the Route 91 Harvest Festival.

The festival, named for the iconic Las Vegas Boulevard, is a showcase for a range of country and western talents from established heavyweights such as headliners Eric Church, Sam Hunt and Jason Aldean to new up and comers.

Related: Las Vegas Shooting Live Updates: Several Dead, More Than 20 Injured After Attack Near Mandalay Bay Casino

The Mandalay Bay Resort and Hotel, the location for this year's festival, is situated in the heart of the Las Vegas Strip. The four star casino and hotel can be found on the south side of the Boulevard.

More than 40,000 fans were expected to see the different acts which also included Lauren Alaina, Big & Rich, Lee Brice, Kane Brown, Brothers Osborne, Josh Abbott Band, Maren Morris and Brett Young.

Dozens of shots rang out at 22:30 p.m. local time (1:30 a.m. ET) as the festival's final headline act, Jason Aldean, was performing.

Prior to his set at the Harvest Festival, Aldean said he would give the set everything he had. "We try to go out every night and give everybody what they paid for," Aldean told festival media.

"They may only catch one show a year, and it may be this one. So every show you have to go out and turn it up a notch and give it everything you got," he added. The singer, signed to Broken Bow Records, debuted with his self titled album in 2005. The 40-year-old has had 19 No. 1 country singles.

Praying for everyone here in Vegas. I witnessed the most unimaginable event tonight. We are okay. Others arent. Please pray.

— Jake Owen (@jakeowen) October 2, 2017

According to the most recent reports, 20 people were killed in the shooting and 100 injured. ABC News reported that Aldean and his team escaped the attack unscathed.

Luke Combs who performed before Aldean and the penultimate act of the evening, Jake Owen, confirmed as the shooting was taking place that he was safe. "Praying for everyone here in Vegas. I witnessed the most unimaginable event tonight. We are okay. Others aren't. Please pray," he later tweeted.

Festival tickets cost $210 for all three days. The 2017 event was the fourth time the festival had been held in Las Vegas.