Washington - US President Donald Trump decried the massacre of at least 58 Las Vegas concert goers as an "act of pure evil" on Monday, but refrained from addressing calls for gun control or an unproven claim of responsibility from the ISIS group. Delivering televised remarks from the White House, Trump ordered that flags be flown at half-staff until sunset on Friday, offered prayers for the victims and announced he would visit Las Vegas on Wednesday. Trump did not address an ISIS propaganda agency's unverified claim that one of its "soldiers" who had "converted to Islam" months ago was responsible. However, the FBI says it has so far found "no connection" between international terrorist groups and the Vegas attack. White House officials also refused to comment on that claim "at this point" saying the local authorities' investigation was "ongoing". Calling for unity, Trump instead tried to console the nation - an act that has become a grim rite of passage for modern US presidents as each mass shooting rekindles the divisive national debate on gun control. "In moments of tragedy and horror, America comes together as one - and it always has," Trump said."Our unity cannot be shattered by evil. Our bonds cannot be broken by violence. And though we feel such great anger at the senseless murder of our fellow citizens, it is our love that defines us today - and always will, forever." But in the immediate aftermath of the shooting, that unity was difficult to find. 'Right to bear arms' Police have identified the heavily armed gunman behind the Sunday night massacre in Las Vegas - the deadliest mass shooting in modern US history which left more than 500 injured - as a 64-year-old Nevada resident named Stephen Craig Paddock. Paddock apparently killed himself before a SWAT team breached his hotel room overlooking the concert venue, recovering at least eight rifles. Trump's vanquished election rival Hillary Clinton hit out at the gun manufacturers lobby - the National Rifle Association - which has backed a congressional push to make it easier to obtain a gun silencer. "The crowd fled at the sound of gunshots. Imagine the deaths if the shooter had a silencer," tweeted Clinton, whose Democratic Party has tried in vain to introduce lasting gun control measures despite the national scourge of mass shootings.Las Vegas, we are grieving with you—the victims, those who lost loved ones, the responders, & all affected by this cold-blooded massacre.— Hillary Clinton (@HillaryClinton) October 2, 2017The crowd fled at the sound of gunshots. Imagine the deaths if the shooter had a silencer, which the NRA wants to make easier to get.— Hillary Clinton (@HillaryClinton) October 2, 2017Our 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.— Hillary Clinton (@HillaryClinton) October 2, 2017"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."The issue of gun control is highly sensitive in the United States and Trump's own views on the issue have changed markedly over his years in public life. After the 2012 Sandy Hook Elementary School shooting, where 20 children and six adults were mowed down by a disturbed 20-year-old, Trump appeared to favour stricter rules. Back then, former US president Barack Obama - who often called Sandy Hook the worst moment of his eight-year presidency and recalls even his Secret Service detail in tears - called for the deadlock to be broken and for congress to act. At that time Trump tweeted: "President Obama spoke for me and every American in his remarks in #Newtown Connecticut." But since then, Trump - whose White House bid was eagerly endorsed by the NRA - has positioned himself as a staunch defender of the constitutional "right to keep and bear arms". US Senator Chris Murphy, who was the congressman for Sandy Hook, renewed a call for action in the wake of the Las Vegas attack. "Nowhere but America do horrific large-scale mass shootings happen with this degree of regularity," he said. "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." 'Pretty much like a war scene' Witnesses said Paddock opened fire with an initial long burst of gunfire and then appeared to reload as he continued his spree. "We heard [what] sounded like a glass breaking, so you looked around to see what's going on and then heard a pop, pop, pop," Monique Dekerf told CNN."You'd think for a moment okay we're fine, there's no more gunfire, then it starts again."At least 50 dead as Mandalay Bay Las Vegas shooting becomes worst in U.S. history https://t.co/5yEz2R8C8I pic.twitter.com/VFcoZY4EAg— TIME (@TIME) October 2, 2017 Country music star Jason Aldean was on stage and near the end of his concert when the shooting began. Aldean initially carried on playing when the first crackle of gunfire could be heard but then hurried off the stage. Robert Hayes, a firefighter from Los Angeles who was in front of the stage, said he first thought the shots were some kind of equipment malfunction. Once he realized what was going on, he joined the first responders, donning one of their vests. "Honestly I probably pronounced 15-20 people" dead, he told Fox News. "It was pretty much like a war scene inside." Emergency crews used anything to hand as makeshift stretchers, including tables and metal railings normally used to control the crowds, said Hayes. Asked if he thought it was an inexperienced gunman, he responded: "With 30 000 people in the arena area, it was kind of like shooting goldfish ... He didn't have to be good." 'Beyond horrific' The Las Vegas attack is the deadliest shooting in recent US history, exceeding the toll of 49 dead in an attack on the Pulse nightclub in Orlando, Florida in June 2016. It was also the latest in a series of recent deadly attacks at concert venues. Twenty-two people were killed while leaving an Ariana Grande concert in the northern English city of Manchester in May when a suicide bomber detonated a nail bomb in the foyer. Ninety people were killed in November 2015 at the Bataclan venue in Paris during a concert by US band the Eagles of Death Metal. A shocked Aldean told his fans via Instagram that he and his band was safe. "Tonight has been beyond horrific," the singer wrote. "It hurts my heart that this would happen to anyone who was just coming out to enjoy what should have been a fun night." Pope Francis said he was "deeply saddened" by the "senseless tragedy" while Britain's Prime Minister Theresa May called it an "appalling attack."