President Donald Trump addressed the nation Monday morning hours after a gunman killed at least 59 people at a country music concert in Las Vegas, saying he would visit the city on Wednesday.
"We are joined together today in sadness, shock and grief," Trump said. "It was an act of pure evil."
The President also thanked first responders in Las Vegas, saying that "the speed with which they acted was miracoulous."
He also addressed the families of those killed and wounded in the attack, saying "we are praying for you, and we are here with you.
Trump also ordered that the American flag be flown at half-staff in mourning of those wounded and killed at the concert.
"Even the darkest space can be brightened by a single light," Trump said.
Earlier on Monday morning, Trump tweeted "My warmest condolences and sympathies to the victims and families of the terrible Las Vegas shooting. God bless you!"
Press secretary Sarah Huckabee Sanders called the shooting a "horrific tragedy" in a statement.
"We are monitoring the situation closely and offer our full support to state and local officials," Sanders said. "All of those affected are in our thoughts and prayers."
White House chief of staff John Kelly briefed the President on the shooting, she said.
An administration official told CNN the President's trip to Puerto Rico to survey the hurricane response there, which was planned for Tuesday, is now under review.
Vice President Mike Pence issued a statement on Twitter, saying he and his wife were praying for the victims.
Ivanka Trump, the President's eldest daughter and a top adviser, tweeted "our collective hearts are breaking for the victims and their families."
Nevada politicians also responded Monday morning to the massacre, decrying the violence and offering thanks to first responders.
"Senseless, horrifying act of violence in Las Vegas tonight," Republican Sen. Dean Heller tweeted. " Praying for all the victims & those impacted by the tragedy."
"Thankful for police and first-responders on the scene," Heller said.
Heller said he had spoken with Nevada Gov. Brian Sandoval and state Attorney General Adam Laxalt.
Democratic Sen. Catherine Cortez Masto offered prayers to the victims and thanks to the first responders on Twitter.
"Praying for all those affected by this senseless tragedy. Thank you to all the first responders. I will continue to monitor the situation," Cortez Masto tweeted.
Sandoval, a Republican, called the shooting a "tragic & heinous act of violence" and offered his prayers.
"A tragic & heinous act of violence has shaken the #Nevada family. Our prayers are w/ the victims & all affected by this act of cowardice," Sandoval tweeted.
Members of Nevada's House delegation offered their thoughts as well.
Democratic Rep. Ruben Kihuen thanked the first responders in a tweet, and Rep. Dina Titus, also a Democrat, said in a statement that her "heart aches for the victims, their loved ones and our community."
As the morning wore on, politicians from around the country extended their sympathies to the victims of the shooting and thanks to first responders.
Florida Republican Sen. Marco Rubio, whose state suffered a massive shooting in an Orlando nightclub last year, tweeted his prayers, and Connecticut Democratic Sen. Chris Murphy, who has kept up a drumbeat for gun control in response to the Sandy Hook Elementary School shooting in his state in 2012, tweeted, "Not again."
House Minority Leader Nancy Pelosi wrote on Twitter that she was "horrified and heartbroken."
Foreign leaders sent their condolences on the shooting Monday morning. United Kingdom Prime Minister Theresa May responded on Twitter, as did London Mayor Sadiq Khan.
"PM -- The UK's thoughts are with the victims and the emergency services responding to the appalling attack in Las Vegas," May tweeted.
Khan tweeted, "A deeply sad day for the city of Las Vegas. London sends our condolences to the victims and their families."
Police said in the early hours of Monday morning that the suspected gunman, identified as Stephen Paddock, 64, killed himself before law enforcement entered the room.