Story highlights Trump spoke about the attack from the Diplomatic Reception Room

It is the deadliest mass shooting in US history

Washington (CNN) President Donald Trump used a solemn address from the White House on Monday to call for unity in the aftermath of the deadliest mass shooting in modern US history, calling the massacre an "act of pure evil."

The gun attack on a country music festival Sunday in Las Vegas killed at least 50 people and injured more than 400 others.

In a subdued statement, Trump said the nation was united "in sadness, shock and grief."

Reading from a teleprompter in the Diplomatic Reception Room, Trump mourned the victims and announced he would visit the stricken Nevada city on Wednesday.

"We cannot fathom their pain, we cannot imagine their loss," Trump said of those who lost loved ones in the massacre.

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