Updated at 11:45 a.m. ET
A gunman who fired upon thousands of people attending a music festival on the Las Vegas Strip has killed at least 58 people, police say. Some 515 people were injured in the mass shooting and panic that ensued. At least one of the dead is an off-duty police officer who was attending the concert.
The suspect in the case is also dead. Police say they're still trying to learn what could have motivated such an attack.
"The Clark County Fire Department estimated that approximately 406 people were transported to area hospitals," the Las Vegas Metropolitan Police Department says.
Gunfire at the multi-day Route 91 Harvest concert was reported around 10:08 p.m. Sunday, Clark County Sheriff Joe Lombardo said at a news briefing. He later added that the shooter, acting as a "lone wolf," has been identified as Stephen Paddock, 64, a white male who is a resident of Nevada.
Responding to reports that Amaq, a news outlet associated with ISIS, says that the terrorist group claimed responsibility for the attack — and that Paddock had converted to Islam — FBI Las Vegas Special Agent in Charge Aaron Rouse said that the agency has "determined, to this point, no connection with an international terrorist group."
Local officials asked people to donate blood through United Blood Services — and a massive response followed, with long lines prompting the service to deploy mobile donation vehicles and open more facilities to the public. Others showed up to offer water and snacks to people waiting in line, local Fox 5 News reports.
Police say Paddock fired down at the crowd of more than 22,000 people from his room on the 32nd floor of the Mandalay Bay Resort and Casino. A SWAT team used an explosive to breach the room, Lombardo said. When police entered the room, they "found the suspect dead," Las Vegas police say.
Police say they believe Paddock killed himself. Lombardo said "in excess of 10 rifles" were found in the room; he did not identify the guns other than to call them rifles. He later added that information suggests the suspect had been in the hotel room since Thursday.
The violence is now being called the deadliest mass shooting in modern U.S. history, and the tragic death toll seems likely to rise. Forty-nine victims were killed in the June 2016 mass shooting at the Pulse nightclub in Orlando, Fla.
Images and video from the Las Vegas Strip are harrowing. They show masses of people screaming and trying to seek safety as torrents of gunshots echo through the area of Las Vegas Village, an outdoor venue northwest of the Mandalay Bay Resort and Casino — where the gunman was positioned on the 32nd floor, police say.
Witnesses said that at first they thought the gunshots were fireworks. After the danger became clear, several said, they were still unsure where to run — because they couldn't see where the bullets were coming from.
Two on-duty police officers were injured during the shooting, the department says, adding, "One is in stable condition after surgery and the other sustained minor injuries."
"Obviously this is a tragic incident, and one that we've never experienced in this valley," Lombardo said. One goal now, he said, was to "get our first responders back on their feet" and conducting a full investigation.
The sheriff also shared the number of a hotline people can use to check on their loved ones: a missing persons hotline at 866-535-5654.
President Trump said via a tweet, "My warmest condolences and sympathies to the victims and families of the terrible Las Vegas shooting. God bless you!"
In a White House address delivered shortly before 11 a.m. ET Monday, Trump said he will visit Las Vegas on Wednesday. He also said he has ordered the flag to be flown at half-staff.
"In moments of tragedy and horror, America comes together as one — and it always has," Trump said.
Little is known about the suspected gunman. As Casey Morell of member station KNPR reports about Paddock, "He lived in a town called Mesquite — which is about 90 minutes north of Las Vegas" in Clark County.
Investigators "have conducted a search warrant" at Paddock's residence," the Mesquite Police Department said. Lombardo later added that other properties will also be searched.
Paddock seems not to have had a criminal record. "The only thing we can tell is he received a citation several years ago and that citation was handled as a matter of normal practice in the court system," Lombardo said.
In the initial hours after the shooting, the Las Vegas Metropolitan Police Department said they were looking for Paddock's female companion, Marilou Danley. Early Monday, the department said, "we are confident we have located the female person of interest" — but they later clarified that they believe she was not involved. Lombardo says she was found "out of the country" and that Paddock had used some of her identification.
Police have also located two vehicles associated with Paddock: a Hyundai Tucson and a Chrysler Pacifica.
A Jason Aldean concert was underway at the time of the shooting. On social media, Aldean said he and his crew are safe.
In an Instagram post he called the shooting "beyond horrific."
The mass shooting prompted panic and a lockdown at hotels along the Strip, as a barrage of gunfire rained down on the crowd.
Musician Jake Owen, who played on the same stage as Aldean earlier Sunday night, told CBS News that the stream of gunfire seemed to go on for at least six minutes and possibly as many as 10. He took shelter behind a car with a crowd of other people, he said.
The Associated Press describes the scene:
"Concert-goers reported seeing muzzle flashes from the upper floors of the Mandalay Bay Hotel and Casino across Las Vegas Boulevard from the country music festival and the sound of what they described as automatic gun fire.
"Witnesses said they saw multiple victims as they fled the gunfire raining down on the concert venue.
"Some later huddled in the basement of the nearby Tropicana hotel-casino.
"Some officers took cover behind their vehicles while others carrying assault rifles ran into the Mandalay Bay Hotel and Casino."
Tens of thousands of people attended the weekend-long Route 91 Harvest country music festival. Aldean was headlining the final night of the three-day concert; he had been scheduled to go on stage just before 10 p.m.
The killing of dozens of innocent people has prompted questions about how to define the horrible crime — particularly whether it could most accurately be called domestic terrorism.
When asked about that distinction, Lombardo said, "We have to establish what his motivation is first. And there's motivating factors associated with terrorism other than a distraught person just intending to cause mass casualties."
Paddock's brother Eric, who lives in Orlando, Fla., says the family doesn't know why Paddock might carry out a deadly shooting.
"We have absolutely no idea whatsoever," Eric Paddock said to reporters gathered outside his home Monday morning. "We have no idea why he did this. And that's what you're going to find out. I can't imagine. When you guys found out why this happened, let us know. I have no idea whatsoever."
Visibly distraught, Eric Paddock said the family sends its condolences to everyone affected by the attack. He said he was "dumbfounded" after being told that his brother had killed dozens of people. As for the guns Stephen Paddock reportedly used, Eric Paddock noted that his brother doesn't have a military background and asked, "Where the hell did he get automatic weapons?"
Eric Paddock described the suspect as someone who gambled in Las Vegas casinos, enjoyed burritos, and dated a woman who sent cookies to their mother. The last contact between the two, he said, was when Stephen Paddock texted to check on his family after Hurricane Irma hit Florida.
The FBI is assisting with the investigation, including helping to process evidence from the scene, Lombardo said. He added that the Red Cross is also helping the community.
Flights in and out of nearby McCarran International Airport were temporarily halted, but some flights resumed early Monday.
This is a developing story. Some things that get reported by the media will later turn out to be wrong. We will focus on reports from police officials and other authorities, credible news outlets and reporters who are at the scene. We will update as the situation develops.