WASHINGTON, Oct. 2 -- U.S. President Donald Trump on Monday called a mass shooting at a Las Vegas concert that has killed more than 50 an "act of pure evil," adding that he will visit the city on Wednesday.

"In memory of the fallen, I have directed that our great flag be flown at half-staff," Trump said in a televised statement.

"I will be visiting Las Vegas on Wednesday to meet with law enforcement, first responders and the families of the victims," Trump said.

Earlier Monday, Trump tweeted his "warmest condolences and sympathies to the victims and families" of the shooting.

The U.S. Department of Homeland Security said earlier that investigation was underway.