Washington appears to be moving closer to new gun rules.
On Capitol Hill, support appeared to grow for a ban on the bump stock devices, either through regulation or legislation, as Republicans — who for decades have rejected any form of gun restrictions — began increasingly to speak out. Several leading Republicans, including Senator John Cornyn, the No. 2 Republican in the Senate, have raised serious questions about the devices.
In the House, Representative Carlos Curbelo, Republican of Florida, has drafted a measure banning bump stocks, which he said he planned to introduce on Thursday. He said his office had been “flooded” with calls from dozens of fellow Republicans who wanted to sign on.
“I think we are on the verge of a breakthrough when it comes to sensible gun policy,” Mr. Curbelo said.
His comments followed those of House Speaker Paul D. Ryan, who during an interview with MSNBC also raised questions about the conversion kits, and said he was open to legislation. “Clearly that’s something we need to look into,” Mr. Ryan said.
Separately, Representative Adam Kinzinger, Republican of Illinois, is circulating a letter among his colleagues, calling on the A.T.F. to re-evaluate bump stocks, which he said had “no place in civilized society.”
The fire chief wondered, ‘Are we under a Mumbai-style attack?’
Chief Greg Cassell of the Clark County Fire Department said on Thursday that several factors complicated the department’s response to the mass shooting, but he praised the emergency responders as heroic.
“We had a lot of challenges with this event,” Mr. Cassell said at a news conference. Wounded concertgoers fled to various hotels and called 911 from there, he said. “By the time it got relayed, it was ‘There’s a shooter at this location,’” he said. “It was, ‘People were shot.’”
Typically, all 911 calls from a single event would be linked, he said. But because of the confusion on Sunday night, operators logged the calls as coming from 32 separate incidents, each of which needed to be investigated. Mr. Cassell said they wondered, “Are we under a Mumbai-style attack, where we’ve got multiple things going on at multiple properties?”
He was referring to a group of coordinated terror attacks in Mumbai, India, in November 2008, when gunmen stormed two hotels, a railroad station, a restaurant, a hospital and a Jewish center; 160 people were killed.
Mr. Cassell said that as crews were heading to the concert area in Las Vegas, they encountered injured people in every direction, so they stopped, aided those patients and called for more help, rather than continuing to the site of the shooting.
He said a total of 160 members of local fire departments responded to the emergency. Only one was hurt, suffering a minor injury from a fall.
“We’ve been somewhat planning on a major event in our valley for an awful, awful long time along these lines,” he said. “We never planned on what happened the other night.”
The gunman’s girlfriend said she was unaware of the plan.
In her first public statement since the shooting, the gunman’s girlfriend said on Wednesday that he had sent her on a trip to the Philippines and wired her money there, but that she did not know he had been planning to harm anyone.
The statement from the woman, Marilou Danley, which was read by her lawyer, Matthew Lombard, came after Ms. Danley went to the Los Angeles offices of the F.B.I. for questioning, according to a law enforcement official. It was released as the authorities sought her insight into what prompted a man with no evident criminal history to become a mass murderer.
She stressed that she returned to the United States voluntarily, “because I know that the F.B.I. and the Las Vegas police department wanted to talk to me, and I wanted to talk to them.”
“He never said anything to me or took any action that I was aware of, that I understood in any way to be a warning that something horrible like this was going to happen,” she said.
The gunman booked accommodations near another festival.
The gunman’s motive remains unknown, Sheriff Lombardo said on Wednesday. Despite the meticulous planning that went into the attack, the gunman left behind few obvious traces, with no social media footprint to examine or manifesto to be pored over, he said.
The sheriff indicated that Mr. Paddock may have blended in intentionally, hiding the urge to violence that drove him to one of the deadliest mass shootings in modern United States history.
“Anything that would indicate this individual’s trigger point, that would cause him to do such harm, we haven’t understood it yet,” the sheriff said. “Don’t you think the concealment of his history, of his life, was well-thought-out?”
Investigators continue to piece together the life and mind-set of a gunman who had no apparent history of violence. “What we know is Stephen Paddock is a man who spent decades acquiring weapons and ammo and living a secret life, much of which will never be fully understood,” the sheriff said.
Mr. Lombardo said that a few days before the shooting, the gunman took another set of rooms in a high-rise building near another music festival. Through Airbnb, he rented a unit in the Ogden, a condominium building in downtown Las Vegas with a view of the Life Is Beautiful festival, held from Sept. 22 to Sept. 25.
At least three of the rifles Mr. Paddock had in his luxury suite on the 32nd floor of the Mandalay Bay Resort and Casino were equipped with scopes.