A gunman opened fire at the outdoor Route 91 Harvest Festival on the Las Vegas strip on Sunday night, leaving 58 people dead and 515 injured, according to reports. The shooting started just as Jason Aldean began his headlining set, sending him running from stage for cover as the tragedy unfolded.

Aldean assured fans he was safe while breaking his silence on the shooting in an emotional Instagram post early Monday morning. “Tonight has been beyond horrific,” he wrote. “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.”

Other country artists who were at the event, such as Jake Owen and Chris Young, shared their horrific first-hand experience of the shooting.

Many celebrities took to Twitter to share their shock and sadness, while sending their thoughts to those involved. Both Celine Dion and Mariah Carey, who have spent a lot of time on the strip doing concert residencies in Las Vegas, sent prayers to the victims and their families.

George Takei took a moment to thank the Las Vegas first responders, while others urged those who can to donate blood.

While Julianne Moore spoke out about ending gun violence.

Many found themselves in disbelief over the events, unable to find the appropriate words for the situation. “WTF is happening,” Bob Saget wrote. “Can’t keep up with all the pain this country is facing.”

Police report that the suspect, Stephen Paddock, 64, of Mesquite, Nevada, fired at the festival from the 32nd floor of the Mandalay Bay hotel before shooting himself.

Our thoughts are with the victims and their loved ones.

(Photo via Mark Ralston/AFP/Getty)