The death and injury count has risen, Clark County Sheriff Joe Lombardo told reporters Monday evening: 59 people have died and 527 are injured.
He added 18 firearms, explosives, and several thousand rounds of ammunition were recovered at the shooter’s home on Monday, on top of the weapons that were uncovered with the shooter in his Mandalay Bay hotel room. Electronics were also seized from the shooter’s home and are being evaluated.
Authorities later said they'd found 23 firearms in Paddock's room and 19 at his home.
In addition, Clark County has declared a state of emergency in the wake of the shooting.
NEW: Clark Co., Nevada, which includes Las Vegas, declares a state of emergency after concert mass shooting attack. pic.twitter.com/qG3F7M2Bwr
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There’s plenty we still don't know about the massacre in Las Vegas that killed at least 59 and injured more than 500. Authorities have said those numbers could increase; meanwhile, the identifies of the victims are still mostly unknown. For continuing coverage throughout the night, check NBCNews.com and tune into MSNBC.
Here's What We Know, as of Monday Evening
The death toll ticked up to 59, while the number of injured rose to 527.
Gunman Stephen Paddock had 19 firearms, several thousand rounds of ammunition and explosives in his home, according to investigators, in addition to 23 weapons found in his Mandalay Bay hotel room on the 32nd floor.
Two Nevada gun shops confirmed that they sold firearms to Paddock in the last year and said he passed all required background checks. It's not clear whether those weapons were used in Monday's massacre.
Paddock spent "tens of thousands of dollars" gambling in Las Vegas casinos in recent weeks, law enforcement officials told NBC News. It's unclear whether if he was winning or losing money off those large transactions.
It took 72 minutes from the first 911 call for police to locate the shooter, NBC News reported.
There is no apparent link between Paddock and any international terrorist groups, the FBI said.
Here's Some of What We Don't Know
Identities of many of the 59 victims.
Paddock's motive. In interviews with NBC News, members of his family have maintained no history of mental illness, nor any religious or political motivation.
More about Marilou Danley, said to be Paddock's companion and roommate. She was initially named as a person of interest in the investigation, but after she was located out of the country, police said they believed she was not involved. However, the sheriff said they had more questions for her.
Magellan Health has launched a 24-hour crisis line for victims of the shooting, offering free, confidential counseling services for affected individuals dealing with grief, guilt, depression, and other feelings related to these events, the behavioral health care firm said in a press release.
Magellan's website also includes free tip sheets for things like talking with children about traumatic events.
The gunman's spot on the 32nd floor of the Mandalay Bay Resort and Casino gave him an unobstructed and protected view of thousands at the Route 91 Harvest festival at the Las Vegas Village, and was effectively a sniper's perch, according to MSBNC law enforcement analyst Jim Cavanaugh.
“Funds will be used to provide relief and financial support to the victims and families of the horrific Las Vegas mass shooting,” Clark County Commission Chairman Steve Sisolak, who established the fund, wrote on the page.
Sisolak, also a gubernatorial candidate, said he spent Sunday night with the sheriff at a local trauma center. He kicked off fundraising with a $10,000 donation. According to the GoFundMe, the Oakland Raiders also donated $50,000.
David Becker, a Getty Images photographer, was transmitting his concert photos when a gunman opened fire on the crowd. He didn't leave when he saw people fleeing.
Instead, he got up on a table with his camera, "thinking to myself still, that this isn’t really happening, it’s just the speakers popping."
"I was trying to capture anything that was moving and that had good lighting. That was critical, it was so dark and there was limited lighting it was really hard to get a sense of what was happening," he told NBC News in a statement.
Awareness would dawn a little later. He started editing his photos back at the media tent before eventually being escorted from the scene.
"It was then I started looking at my photographs and what I was seeing was just unbelievable. It had been so dark outside I couldn’t see the details, I just saw a lot of people laying on the ground thinking they were playing possum, but now I could see people covered in blood and I thought, this is real. When I saw the image of the woman lying on the ground covered in blood, that was when the impact of what I was experiencing hit; when I realized people were dying."
“As much as we might hope to we cannot banish evil from the earth, Congress can't do that, the president can't do that,” he said from the Senate floor. “What Congress can do, what Congress must do, is pass laws to keep our citizens safe.”
“And that starts with guns, especially laws that help prevent guns, especially the most dangerous guns from falling into the wrong hands,” Schumer continued.
His impassioned remarks followed a more subdued statement from his counterpart, Senate Majority Leader Mitch McConnell, R-Ky., who also spoke from the chamber floor but did not reference guns.
“The news we awoke to this morning was heartbreaking. What happened in Las Vegas was shocking, it’s tragic, and for those affected, and their families, it’s devastating,” McConnell said.
“I hope they will see that our country is standing by their side today,” he added.
Pop star Ariana Grande — who experienced firsthand the terror of a tragic attack at one of her own concerts in Manchester, England, earlier this year — called Monday's shooting "terrorism" and made a plea for gun control.
“My heart is breaking for Las Vegas. We need love, unity, peace, gun control & for people to look at this & call this what it is = terrorism,” Grande tweeted Monday afternoon.
The American singer's post came just over four months after the May 22 Manchester Arena bombing that occurred right after she’d finished a concert at the venue. Children were among the 22 people killed in the suicide attack, while some 59 others were wounded, including some who suffered life-threatening injuries.
My heart is breaking for Las Vegas. We need love, unity, peace, gun control & for people to look at this & call this what it is = terrorism.
The president believes that now is not the time to talk about gun control in the immediate aftermath of the deadliest mass shooting in modern American history, the White House said Monday.
Asked about renewed pleas from lawmakers for stricter gun control measures, White House Press Secretary Sarah Huckabee Sanders said it was "premature" to talk about potential legislation before all the facts about the Las Vegas mass shooting are known.
"There's a time and place for a political debate, but now is the time to unite as a country," Sanders said,