Story highlights Attack occurred during a music festival

Celebrities have been tweeting their support

(CNN) Celebrities offered sympathy and support for Las Vegas after the massacre that left at least 50 people dead.

A gunman opened fire from the 32nd floor of the Mandalay Bay hotel into a country music festival on the ground, authorities said. At least 200 people were injured.

Country singer Jason Aldean, who was performing on stage at the time, expressed sorrow on Instagram and asked that his fans "Pray for Las Vegas."

"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."