WASHINGTON - As the United States reeled from the deadliest mass shooting it has ever seen, politicians in Washington on Monday offered condolences and vowed thorough investigation into the tragedy.

US President Donald Trump tweeted early morning after being briefed on the shooting, "My warmest condolences and sympathies to the victims and families of the terrible Las Vegas shooting. God bless you!"

Hours after the tweet Trump appeared on television and delivered a somber remark, calling the shooting "an act of pure evil."

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

Following his order, flags around Washington D.C. including in the national mall, can be seen flying at half-mast.

Trump also announced a visit to the wounded city on Wednesday "to meet with law enforcement, first responders and the families of the victims," following his scheduled visit to the hurricane devastated island of Puerto Rico Tuesday.

In the afternoon, Trump and the first lady led a moment of silence on the White House south lawn, in remembrance of those unfortunate.

The sentiment was shared on Capitol Hill, as multiple members of Congress also offered their sympathies.

"We are with you during this time. The whole country stands united in our shock, in our condolences, and in our prayers," House Speaker Paul Ryan said in a statement.

Amid the condolences questions are quickly being raised on gun control, a recurring debate in the United States that followed each mass shooting the country has recently seen.

When asked about whether the administration is considering gun regulation reform, White House Press Secretary Sarah Sanders said in a press briefing Monday that it was too early for such discussions.

"Today is a day for consoling the survivors, and mourning those we lost...there's a time and place for a political debate, but now is the time to unite as a country," an emotional Sanders told the briefing.

"There is currently an open and ongoing law enforcement investigation. A motive is yet to be determined. And it would be premature for us to discuss policy when we don't fully know all the facts, or what took place last night," she said.

"I think that there will be, certainly, time for that policy discussion to take place. But that's not the place that we're in at this moment," she added.

Despite the hesitation from the White House, left-wing politicians unanimously called for more gun regulations.

Hillary Clinton, the Democrat's presidential nominee in 2016, launched a pointed attack against the National Rifle Association (NRA), a major lobby group for gun rights.

"Imagine the deaths if the shooter had a silencer, which the NRA wants to make easier to get," she said, adding "our grief isn't enough. We can and must put politics aside, stand up to the NRA, and work together to try to stop this from happening again."

Her voice was echoed by Democratic Senator from the state of Connecticut Chris Murphy, whose constituency saw the tragic Sandy Hook Elementary School shooting in 2012 which killed 28 people, including 20 children.

"This must stop. It is positively infuriating that my colleagues in Congress are so afraid of the gun industry that they pretend there aren't public policy responses to this epidemic," he said in a statement.

Murphy pointed out that the number of mass shootings in the US so far this year has averaged more than once a day.