Country music stars, some who witnessed the deadly shooting at the Route 91 Harvest festival in Las Vegas, are reacting following what is now thought to be the worst mass shooting in U.S. history.

Tonight has been beyond horrific. I still dont 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

A post shared by Jason Aldean (@jasonaldean) on

More than 50 people were killed and over 200 injured when a "lone wolf" gunman opened fire on people attending the three-day country music festival, police said.

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The three-day Route 91 Harvest festival started Friday and is reported to have attracted 30,000 attendees. The shooting occurred on the final night, during a performance by Jason Aldean. Aldean confirmed that he and the rest of his team were safe.