LAS VEGAS - Investigators struggled Tuesday with a chilling but baffling array of clues in the wake of the deadliest mass shooting in modern American history - including a hotel room arsenal fit for a commando team - yet were still left trying to explain the chain of events that caused a 64-year-old retiree to turn a concert ground here into a killing field.
"I can't get into the mind of a psychopath," said Joseph Lombardo, the sheriff of the Las Vegas Metropolitan Police Department, on Monday.
At the same time, the probes stretched from a ranch-style home near the Arizona border to the 32nd-floor hotel suite used by Stephen Paddock as a place to scan the crowds at a country music festival and then open fire - leaving at least 59 people dead and hundreds more injured in the rain of bullets or trampled in the panicked rush for cover late Sunday. He then killed himself as SWAT officers closed in.
And once again, a stunned nation was left to grapple with a city riven by tragedy and a resurgent debate over gun control and gun violence. The White House and many Republicans said it was a time to mourn rather than launch into political battles, while some Democrats renewed calls for gun safety legislation.
Lombardo warned that the number of dead in Las Vegas could rise, as an additional 527 were thought to have been injured. Hospitals across the region continued to treat patients from the scene, many of them seriously injured. Sunrise Hospital and Medical Center said that as of Tuesday morning, it had 68 patients from the rampage, 33 of them in critical condition.
While the nation learned more about the lives cut brutally short as well as the heroic actions of people on the ground, few answers were available as to what, if anything, may have motivated the rampage.
Authorities described a level of preparation that suggested the attack was planned in advance. Police said Paddock arrived on Thursday, three days before the shooting, at the Mandalay Bay Resort and Casino on the southern end of the Las Vegas Strip. He took more than 10 suitcases into his suite, officials said.
Paddock aroused no suspicion from hotel staff even as he brought in 23 guns, some of them with scopes. One of the weapons he apparently used in the attack was an AK-47 type rifle, with a stand used to steady it for firing, people familiar with the case said.
Authorities said a sweep of law enforcement databases showed Paddock had no known run-ins with police. Paddock was the son of a bank robber who was once on the FBI's most-wanted list, but investigators have turned up no clear links to any criminal enterprises or international terrorist groups - despite repeated claims by the Islamic State that Paddock carried out the carnage in its name.
Among the questions investigators still have: How a former accountant with a penchant for high-stakes gambling obtained a weapon that sounded to those on the ground like it could fire as an automatic, and how he was able to bring it and many other weapons into a Vegas hotel suite undetected.
Investigators believe at least one of the guns functioned as if it were fully automatic, and they are now trying to determine if he modified it or other weapons to be capable of spitting out a high volume of fire just by holding down the trigger, people familiar with the case said.
Investigators also found at least 19 additional firearms, thousands of rounds of ammunition and the chemical tannerite, an explosive, at Paddock's home in Mesquite, Nevada. They also found ammonium nitrate, a chemical that can be used in bombmaking, in Paddock's vehicle, Lombardo said.
Gun purchase records indicate Paddock legally bought more than two dozen firearms over a period of years, according to a person close to the investigation. Guns & Guitars, a store in Mesquite, Nevada, said in a statement that Paddock purchased some of his weapons there, but employees followed all procedures required by law, and Paddock "never gave any indication or reason to believe he was unstable or unfit at any time." Lombardo said Paddock also seemed to have purchased guns in Arizona.
Police and hotel security scoured several floors of the hotel looking for the shooter and came upon Paddock's suite, Lombardo said. At some point, Paddock fired through the door and hit a security guard in the leg, he said, adding that the guard is expected to survive.
SWAT officers ultimately stormed the room and some fired shots, though Paddock is believed to have killed himself, Lombardo said.
More than 22,000 people had been at the Route 91 Harvest festival, a three-day country music concert with grounds across the street from the Mandalay Bay Resort and Casino, when the shooting began about 10 p.m. Sunday, according to police. As country star Jason Aldean played what was expected to be one of the last sets of the night, Paddock opened fire - his bullets flying from a window on the casino's golden facade, which Paddock had smashed with some type of hammer.
"People were getting shot at while we were running, and people were on the ground bleeding, crying and screaming. We just had to keep going," said Dinora Merino, 28, a dealer at the Ellis Island casino who was at the concert with a friend. "There are tents out there and there's no place to hide. It's just an open field."
The dead included a behavioral therapist who was soon to be married, a nursing assistant from Southern California, a commercial fisherman and an off-duty Las Vegas city police officer. Two other officers who were on duty were injured, police said; one was in stable condition after surgery, and the other sustained minor injuries. Another off-duty officer with the Bakersfield Police Department in Southern California also sustained non-life-threatening injuries, according to a statement from the department.
Syed Saquib, a surgeon on duty Sunday night at University Medical Center, said the hospital treated 104 patients, most of whom had gunshot wounds.
"Those that could be saved, were saved," Saquib said. "There were a few that came in with devastating, non-survivable injuries."
John Soqui drove seven hours from Arizona to see his 29-year-old niece, who had been shot in the head. Jovanna Martinez-Calzadillas, from suburban Phoenix, had been attending the concert with her husband, a military police officer, Soqui said. Her husband, who was not injured, carried Martinez-Calzadillas away from the concert after she had been shot, relatives said.
"There is just so much hate in this world, and she is my little niece, and I just want to get the guy who shot her," said Soqui, 51.
Soqui then remembered that Paddock had apparently taken his own life before police stormed into his hotel room. "I want to die, kill myself, just so I can get him," Soqui added. "So many people have been affected by this, and it's just killing me that there are people like that out there."
President Trump ordered flags flown at half-staff and said he would visit Las Vegas on Wednesday.
Leaving the White House to visit hurricane-ravaged Puerto Rico on Tuesday morning, Trump repeated his praise for police in Las Vegas and their response, saying of law enforcement that "what happened in Las Vegas is in many ways a miracle." He also said that "we'll be talking about gun laws as time goes by."
Eric Paddock, Stephen Paddock's brother, said he was stunned to learn that his brother could be responsible for such violence.
Stephen Paddock had no history of mental illness nor did he have problems with drugs or alcohol, Eric Paddock said, noting that his brother was a high-stakes gambler, sometimes wagering hundreds of dollars on a single hand of video poker.
When he spoke to the FBI, Eric Paddock said he showed agents three years of text messages from his brother, including one that mentioned winning $250,000 at a casino. A federal law enforcement official said investigators had reviewed reports suggesting Paddock engaged in high-dollar gambling, and they are trying to determine whether he faced financial strains.
Eric Paddock said his brother was "wealthy," in part because he had no children to support. Stephen Paddock had worked in the past as an accountant, and he had real estate investments in the Orlando area, Eric Paddock said.
Lockheed Martin, the defense giant, said that Paddock had worked for the company for three years in the 1980s.
Police said they believe Paddock was a "lone wolf" attacker, though they were still interested in speaking more with a woman named Marilou Danley who lived with him in Mesquite, Nevada, a little more than an hour outside of Las Vegas on the Arizona border. Danley, Paddock's 62-year-old girlfriend, was found outside the country - as of Monday afternoon, in Tokyo - and was not involved in the shooting.
"We still consider her a person of interest," Lombardo said Monday. He said investigators also are exploring a report that Paddock attended a different music festival in September.
Not long after the shooting, the Islamic State claimed responsibility, though law enforcement authorities were quick to reject that assertion. "We have determined, to this point, no connection with an international terrorist group," Aaron Rouse, the special agent in charge of the FBI in Las Vegas, said at a news briefing.
Zapotosky and Berman reported from Washington. Lynh Bui, Felicia Mello and Heather Long in Las Vegas; Barbara Liston in Orlando; Justin Glawe in Mesquite, Tex.; and Derek Hawkins, Travis M. Andrews, Brian Murphy, Wesley Lowery and Julie Tate in Washington contributed to this report.