Hillary Clinton criticized the National Riffle Association on Monday morning while offering her condolences to the victims of a mass shooting in Las Vegas this weekend that left at least 50 people dead and more than 400 people injured.

“Our grief isn’t enough,” the former Democratic Party presidential candidate tweeted. “We can and must put politics aside, stand up to the NRA, and work together to try to stop this from happening again.”

Clinton’s statement was one of the most politically charged among prominent politicians who weighed in on social media in the hours after the attack. She writes in her book “What Happened” about how the United States needs to change its gun laws to prevent mass shootings.

Barack Obama and Bill Clinton also tweeted their support for the victims.

“Michelle & I are praying for the victims in Las Vegas,” Obama tweeted. “Our thoughts are with their families & everyone enduring another senseless tragedy.”

“Thinking of the victims and responders in Las Vegas,” Bill Clinton tweeted. “This should be unimaginable in America.”

According to police, 64-year-old Stephen Paddock opened fire on attendees of the Route 91 Harvest Music Festival near the Mandalay Bay Hotel and Casino in Las Vegas on Sunday evening. The victims were apparently shot with a high-powered assault rifle from the 32nd floor of the Mandalay Bay Hotel, with police confirming shortly after midnight that Paddock had been killed in a standoff with authorities.

President Donald Trump offered his sympathy for the victims of the attack, the worst in U.S. history.

“My warmest condolences and sympathies to the victims and families of the terrible Las Vegas shooting,” Trump wrote on Twitter. “God bless you!”