LAS VEGAS (TNS) — At least 59 people were killed and 527 others injured after a gunman opened fire Sunday night at an outdoor country music festival near the Las Vegas Strip — the deadliest mass shooting in modern American history.

The first shots came at 10:08 p.m., about 20 minutes into a performance by country music star Jason Aldean. More than 22,000 concert-goers sought cover as a barrage of what sounded like automatic weapons fire ripped through the crowd, fired from a room on the 32nd floor of the Mandalay Bay hotel across the street.

Police said the suspect, 64-year-old Stephen Paddock, a resident of Mesquite, Nev., had smashed the windows with a hammer-like tool before opening fire. By the time a SWAT team burst into the room, Paddock had killed himself — leaving in the hotel room at least 19 weapons, mostly military-style rifles.

At least one of them had been modified with a legal "bump stock"-style device that allows the shooter to rapidly fire off rounds without actually converting it to a fully automatic weapon, one federal law enforcement source said. Other weapons may have been converted to fully automatic fire, and were still being examined.

A total of 18 more weapons were found in Paddock's car and in his home, along with thousands of rounds of ammunition.

Ammonium nitrate, sometimes used in manufacturing explosive devices, was found in Paddock's vehicle, Clark County Sheriff Joe Lombardo said.

"Right now we believe it's a solo act, a lone wolf attacker," Lombardo said. "We are pretty confident there is no longer a threat." The Las Vegas Metropolitan Police Department is a joint city-county force headed by the sheriff.

Lombardo said authorities had no evidence of a motive. "We don't know what his belief system was at this time," he said.

U.S. Rep. Ruben Kihuen, D-Nev., who received a briefing from the multi-agency, anti-terrorism center, said no new clues have emerged so far in their search of Paddock's home.

"Law enforcement were looking through his computer. They couldn't find a motive. As of a couple of hours ago, there was no motive. That's all we know," he said.

Investigators found fully automatic guns among multiple weapons in Paddock's 32nd-floor Las Vegas hotel room, according to the top Democrat on the House Intelligence Committee, Rep. Adam Schiff of California.

The congressman, who received a briefing from FBI officials in Washington on Monday, said he didn't know if the guns found in the Mandalay Bay Resort room were manufactured to be fully automatic or had been modified. Such weapons fire more than one round with each pull of the trigger.

White House press secretary Sarah Huckabee Sanders grew emotional as she read a statement praising the people who aided victims in the middle of the gunfire.

"What these people did for each other says far more about who we are as Americans than the cowardly acts of a killer ever could," Sanders said, quoting from the Bible's Gospel of John: "There is no greater love than to lay down one's life for a friend."

The militant group Islamic State issued a statement claiming responsibility for the attack, saying the gunman had converted to Islam months ago, though it provided no proof; almost immediately, the special agent in charge of the FBI's field office in Las Vegas, Aaron Rouse, said federal authorities had found no such evidence.

"We have determined, to this point, no connection to an international terrorist group," Rouse said.

"It was an act of pure evil," President Donald Trump said in a televised statement from Washington. The president did not refer to the shootings as an act of terrorism, but said he would travel to Las Vegas on Wednesday — a day after he visits victims of another tragedy, this one the aftermath of Hurricane Maria in Puerto Rico — to meet with first responders and families of the victims.

"We cannot fathom their pain, we cannot imagine their loss. To the families of the victims, we are praying for you, and we are here for you, and we ask God to see you through this very dark period," Trump said.

"Our unity cannot be shattered by evil, our bonds cannot be broken by violence," Trump added, saying that while Americans may be angry, "it is our love that defines us today and always will forever."

Trump, accompanied by first lady Melania Trump, Vice President Mike Pence and his wife, Karen Pence, and a military honor guard, later led a somber moment of silence on the White House lawn for the massacre victims.

Clark County officials declared a state of emergency as investigators undertook the massive task of identifying all the dead and wounded while also trying to learn what motivated Paddock, a real estate investor, gambler and licensed pilot who appears to have had no previous run-ins with the law.

Police raided the home where Paddock lived with his girlfriend, Marilou Danley, in a small retirement community called Sun City Mesquite, tucked among meandering roads and single-story homes about 80 miles northeast of Las Vegas.

Mesquite police said they'd had no prior contact with the gunman — no traffic stops, no citations, "no arrests, nothing," Mesquite Police Department spokesman Quinn Averett said. "It's a newer home, a newer subdivision, a nice clean home, nothing out of the ordinary."

Danley was out of the country when the attack happened but is a "person of interest" in the investigation, Lombardo said. Officials have contacted her and plan to question her when she returns to the U.S.

"Steve had nothing to do with political organizations, religious organizations," said his brother, Eric Paddock, who lives in Orlando, Fla. "No white-supremacist organizations. Nothing as far as I know, and I've known him for 57 years. Something just incredibly wrong happened to my brother."

Eric Paddock said he helped move his brother from Florida to Mesquite, Nev., a couple of years ago. He said Paddock wanted to get away from the heat and humidity of Florida and be closer to Las Vegas, where he liked to gamble.

"He's just a guy who played video poker and took cruises and ate burritos at Del Taco," Eric Paddock said.

Their father, Benjamin Hoskins Paddock, had been wanted on bank robbery charges and was arrested in Las Vegas in 1960, Eric Paddock said in an interview. He tried to run an FBI agent over with his car before he was captured, according to news accounts from the time.

The elder Paddock, who had a wife and four children in Arizona, was placed on the most-wanted list after escaping from a federal prison in La Tuna, Texas, on Dec. 31, 1968, having served eight years of a 20-year sentence.

He was captured in Springfield, Ore., in 1978, having opened a bingo parlor for a nonprofit organization in Eugene, Ore., during his time on the lam. He died in 1998.

Paddock's former brother-in-law, Scott Brunoehler, remembers the gunman as a smart, fun-loving person.

Paddock was a young man thriving in Southern California when he was married to Brunoehler's sister, Sharon, in the 1970s and early 1980s, Brunoehler said in an interview.

"Oh, he was a smart guy, like an accountant or something. He had a good job, he was a great guy actually," Brunoehler said. "We used to go water skiing together."

Brunoehler, 62, said he hasn't spoken to Paddock since he divorced his sister.

Public records suggest that Paddock also owned or co-owned real-estate in California and Texas, according to the Associated Press.

The fact that the gunman was positioned on the 32nd floor of the Mandalay Bay resort and casino overlooking the outdoor concert site made victims particularly vulnerable, law enforcement experts said.

"It is so, so challenging when you have shooter in a very, very high position," said retired Los Angeles Police Department commander Rick Webb, an expert on active shooter scenarios. "It was very well-thought-out on his part. It is a horrible tragedy."

Webb said it takes time to locate a shooter and that Las Vegas is a very challenging backdrop, even for the experienced Las Vegas Metro Police.

The three-day Route 91 Harvest country music festival was underway across Las Vegas Boulevard from the Mandalay Bay when the shooting erupted about four or five songs into Aldean's performance.

"Single shot. Single shot, then a lot of shots," concert attendee Frank Allard said. Many concertgoers didn't initially realize what was going on.

"I thought it was like bottle rockets going off," said Seth Bayles, of West Hollywood, Calif., who was about 50 feet from the stage. "Then we saw people dropping. We saw someone get hit and then we started running."

Aldean was the final act of the Route 91 Harvest festival, while dozens of others had played over the course of the weekend. In numerous tweets, artists communicated with fans and followers, expressing their sorrow and prayers for anyone injured and telling loved ones that they were safe.

Jake Owen, who played the main stage before Aldean, tweeted: "Praying for everyone here in Vegas. I witnessed the most unimaginable event tonight. We are okay. Others aren't. Please pray."

Aldean responded on Instagram:

"Tonight has been beyond horrific," he wrote. "I still don't know what to say but wanted to let everyone know that Me and my Crew are safe. My Thoughts and prayers go out to everyone involved tonight. It hurts my heart that this would happen to anyone who was just coming out to enjoy what should have been a fun night. #heartbroken #stopthehate."

Inside the Tropicana and outside Mandalay Bay on Monday afternoon, signs broadcasted the phone number people could call about their loved ones and about blood donations.

Electric signs outside Mandalay rotated messages. "Our prayers for the victims," one says. "Our gratitude for the brave first responders."