"The FBI and Dept. of Homeland Security is working with local police," Trump says.
Trump thanked first responders for their quick reaction to the scene.
Trump said "we cannot fathom their pain, we cannot fathom their loss," about families who have lost loved ones in the shooting.
To the injured, the President said "we are praying for your full and speedy recovery. We ask God to help you through this very dark period.
"Scripture teaches us, 'The Lord is close to the broken-hearted, and saves those who are crushed in spirit.' We seek comfort in those words, for we know that God lives in the hearts of those who grieve," the President said.
"To the wounded who are recovering in the hospitals, we are praying for your full and speedy recovery."
He says they he has directed flags be flown at half-staff, and that he will be visiting Las Vegas on Wednesday.
Trump says America always comes together as one. "Our unity cannot be shattered by evil." Though we may feel angry, he said, "our love defines us."