Former Rep. Gabrielle Giffords, who has become an anti-gun violence advocate after she was shot in the head during a 2011 "meet-and-greet" event in Arizona, called Sunday night's deadly mass shooting in Las Vegas a "grave tragedy" on Monday.
In a trio of tweets, Giffords said she is "heartbroken" by the news of the shooting, which left at least 50 dead and hundreds more injured during an open-air country music festival.
Two years after Gifford was nearly killed by the lone gunman, she started her nonprofit, Americans for Responsible Solutions. The gunman who shot her killed six people at the scene and wounded 18 others.
Stephen Paddock, 64, has been identified as the suspected gunman in Las Vegas. He died when police stormed his room at the Mandalay Bay Hotel and Casino, from where the shots were fired from a 32nd floor room.