Las Vegas Attack Sends Chills Down Hollywood's Spine: Stars React to Deadliest Shooting in US History
13 Concert and Nightclub Tragedies Before Route 91 Harvest Festival

Celine Dion, Mariah Carey, Mandy Moore, Trey Songz, Sam Smith and Sheryl Crow react to attack during Jason Aldean concert.

At least 50 people were shot and killed at a Jason Aldean concert in Las Vegas late Sunday night, and another 406 were injured in what has become the deadliest shooting in modern U.S. history.

The gunman, 64-year-old local resident Stephen Paddock, opened fire from the 32nd floor of the Mandalay Bay Hotel toward the 22,000-person crowd at the Route 91 Harvest Festival. He was later found dead by officers.

President Donald Trump was among the first to react on Twitter Monday morning. "My warmest condolences and sympathies to the victims and families of the terrible Las Vegas shooting. God bless you," he tweeted.

Aldean took to Instagram almost immediately after the shooting to let the world know he was safe, sharing: "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."

See how Hollywood is digesting the shocking news via social media below.

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