The Life is Beautiful festival featured the Kiwi pop star as well as Chance the Rapper, Muse and Blink-182.
Hundreds of people were injured when Paddock allegedly opened fire from the window of a hotel room on a crowd attending a country music concert in the streets below.
The girlfriend of Las Vegas shooter Stephen Paddock says she saw no signs he was planning "something horrible", and that she is "devastated" by the deaths and injuries he caused when he rained bullets down on an outdoor music concert.
Having started the day by taking off from Washington by calling it "a very, very sad day for me, personally", the president ended it by striking a sombre and stately tone that sits in contrast to his visit to Puerto Rico the day before.
"Please know that you are in our prayers and that our hearts are heavy for the families who have been left heartbroken and without answers", the family said in a statement.
The Las Vegas gunman who killed 58 people and himself in the deadliest mass shooting in modern US history stockpiled weapons and ammunition over decades, and meticulously planned the attack, authorities believe.
Paddock was not known to have served in the military, to have suffered from a history of mental illness or to have registered any inkling of social disaffection, political discontent or radical views on social media.
"To understand the 'why' helps you deal with the tragedy that we've all faced and we've all faced it, so believe me, we want to know why", says FBI special-agent-in-charge Aaron Rouse.
The first shots were fired at 10:05 p.m., Lombardo said at a Wednesday evening press update.
Stephen Paddock, a reputed heavy gambler, allegedly wired nearly $100,000 to the Philippines prior to the shooting in which he took his own life. When officers entered the hotel room, they found Paddock dead. And authorities found two gun stocks that could have let him modify weapons to make them fully automatic.
Trump told reporters Tuesday night that his trip would include spending time with "some of the folks that are recovering, some of the survivors", and seemed emotional as he spoke about the human toll.
SIEGLER: It's legal in Nevada to openly carry long guns, rifles and other guns in public places, including bars and restaurants, pretty much anywhere but in schools or courtrooms. The deaths from smoke inhalations would have been far fewer if the fusible links, a small piece of the ventilation system, had been installed properly and stopped smoke from spreading.
Paddock transferred $100,000 to the Philippines in the days before the shooting, the AP reported. He dismissed questions about gun-control policies, which he hinted on Tuesday might need to be considered, by saying, "We're not gonna talk about that today".
President Trump said that America was a "nation in mourning" on Wednesday and praised the work of first responders, hospital staff, local leaders and the people of Las Vegas.
The hero continued to help police clear rooms even after being shot.
Investigators are trying to trace that money.
Tammy Baldwin: The Orlando shooter used "a weapon of war". George W. Bush and Barack Obama shed tears in the aftermath of tragedy; it'll be interesting to see if Donald Trump is capable of showing similar emotions.
Bruce Paddock told NBC News the family grew up in Sun Valley, California, and his brother earned money from managing apartment buildings with his Florida-based mother. He referred to Paddock as "a very sick man. He was a very demented person".