By Stephanie Petit
October 02, 2017 at 12:24 PM EDT

The biggest names in country music have shared their heartbroken reactions to the Las Vegas shooting that killed at least 50 people and injured at least 200 in what is now the worst mass shooting in U.S. history.

Blake Shelton wrote on Twitter Monday morning to mourn the victims of the tragedy where a gunman opened fire from his hotel room into the Route 91 Harvest Festival, an outdoor country concert.

“My deepest sympathies and prayers to anyone has been affected by the Vegas shooting last night,” The Voice coach said. “I don’t even know anymore… Why?”

Luke Bryan also shared his heartache, writing on Twitter, “Words can’t begin explain my sadness. My family and I are praying for the victims of this tragedy. Truly heartbroken.”

Bryan’s wife Caroline, and Shelton’s girlfriend Gwen Stefani also shared their condolences. “Beyond horrible. So many prayers and thoughts go to the victims, survivors, and those not accounted for yet,” Caroline wrote. “So tragic. Luke, myself, and his whole organization are heartbroken.”

Jason Aldean, the night’s headliner, was performing when the incident began. Videos posted on social media show Aldean singing as very rapid gunfire begins in the background. He can be seen running from stage as he, and the thousands in the crowd, realized what was happening.

Aldean called the scene “horrific,” but said he was safe in an Instagram post early Monday.

“Tonight has been beyond horrific. 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,” he wrote. “It hurts my heart that this would happen to anyone who was just coming out to enjoy what should have been a fun night.”

Aldean’s wife Brittany posted a message on Instagram early Monday saying, “We are safe… our angels were definitely watching over us tonight. No words for what happened… Just horrific. Praying for everyone.”

Several other country artists who were at the event, including Jake Owen, tweeted in the aftermath. Owen had just finished his set and was still on stage when the shooting started. He told the Today show that he ran off the stage and ducked for cover.

“I was crouched down behind a cop car. There was blood on people and you could see a couple of people in the streets that looked like they had been shot,” he said.

Singer Chris Young took to social media as the events were unfolding, clearly shaken.

Dylan Scott and Luke Combs, who had performed earlier in the night, also shared their reactions on Twitter.

Witnesses reported that a gunman continued to rain bullets on the terrified audience. The victims took the short pauses while the shooter reloaded to run to safety, according to NBC News. Many were trapped in the concert venue as police searched for the gunman.

Police SWAT officers found the shooter – identified as Stephen Paddock, 64, of Mesquite, Nevada – dead of a self-inflicted gunshot wound on the 32nd floor of the Mandalay Bay Casino, Sheriff Joseph Lombardo said.

“Right now we believe it’s a solo act, a lone wolf attacker,” Lombardo told reporters early Monday. “We are pretty confident there is no longer a threat.”