Trump thanked May and praised the first responders in Las Vegas for their immediate and continued actions, the White House said in a statement.
At least 58 people were killed and 515 others injured last night when a gunman went on a shooting rampage from the 32nd floor of a hotel on a concert attended by thousands of people.
This is the deadliest shooting incident in modern US history.
Meanwhile in a statement, Canadian Prime Minister Justin Trudeau offered his deepest condolences to those who lost their loved ones and friends in the Las Vegas shooting and prayed for a fast and full recovery for the many injured.
“We stand with the United States, and share their pain and horror at such a senseless and cowardly act of violence,” he said.
“Las Vegas has long been celebrated by people from around the globe, including many Canadians. We grieve with this city and the United States. Such acts only strengthen our resolve to stand together, united. This city is a destination for people from around the world, and we are following up on reports of Canadian victims. Consular officials are in close contact with local authorities,” Trudeau added.
Americans across the country have expressed shock at the tragic incident.
“America woke up this morning to heartbreaking news. This evil tragedy horrifies us all. To the people of Las Vegas and to the families of the victims, we are with you during this time. The whole country stands united in our shock, in our condolences, and in our prayers,” said Congressman Paul Ryan, Speaker of the US House of Representatives.
“This morning, our nation awoke to news of the largest mass shooting in our history. All of America grieves for the innocent men and women whose lives were cruelly cut short by this tragedy, and our prayers are with the families of those wounded and missing,” said Democratic leader Nancy Pelosi.
It is particularly despicable that this attack was carried out during a concert, transforming an evening of music and celebration into a heartbreaking and horrific night of violence, Pelosi said, adding that “Our nation will never allow fear and violence to bow us or break our spirits”.
Communities across the US will feel the pain of this violence personally as several off-duty police officers attended the concert, one of whom was wounded, said House Majority Leader Kevin McCarthy.
Heartbroken by the terror in Las Vegas. Everyone must be outraged at this latest shooting and they must act, Senator Ben Cardin said.
“Congress must act. States must act. Weapons of war should not be in the hands of civilians. We see the deadly results in Las Vegas just as we saw it in Orlando and Blacksburg, San Bernardino, Aurora, Sandy Hook, the streets of Baltimore, and elsewhere across this great country.
“We need to do everything in our power to stop the carnage of these shootings,” Cardin said.
Senator Tom Carper said that it is critical that federal, state and local law enforcement officials work together to get to the bottom of this attack.
“This is yet another brutal reminder that we must be vigilant here at home against threats of terrorism and face the grim reality that our gun safety laws need to be reexamined,” he said.