President Donald Trump has described the gunman who killed 59 people and injured 527 in Las Vegas on Sunday as "a sick man, a demented man".
Speaking at the White House, he said he would look at gun laws "as times goes by" but did not elaborate.
Police are still trying to find out why Stephen Paddock, 64, opened fire on an open-air concert from the 32nd floor of the nearby Mandalay Bay Hotel.
Las Vegas police say there was a high degree of premeditation.
In his latest briefing Clark County Sheriff Joseph Lombardo said: "I'm pretty sure he evaluated everything he did in his actions."
Mr Lombardo also revealed that Paddock had set up cameras inside and outside his hotel suite, including one on a service cart, to monitor the police.
The sheriff added that the firing had continued for approximately nine minutes.
Police still consider the woman thought to have been his girlfriend, Marilou Danley, "a person of interest", he said. She is in the Philippines. "We are in conversation," Sheriff Lombardo said.
Police found 23 guns in Paddock's hotel room and firearms and explosives at his home.
Photos from the hotel room of guns used in the attack have been obtained by Boston 25 News.
Guns seen on the hotel room floor
As yet, no clear reason for the killing has emerged and investigators have found no link to international terrorism. Some investigators have suggested Paddock had a history of mental illness, but this has not been confirmed.
Paddock, who appears to have killed himself before police stormed his hotel room, had no criminal record and was not known to police.
Speaking to reporters as he was about to board the presidential helicopter, Mr Trump said Paddock was "a sick man, a demented man. Lot of problems, I guess, and we're looking into him very, very seriously".
When asked, Mr Trump declined to call the attack domestic terrorism.
On the issue of gun control, the president said: "We'll be talking about gun laws as time goes by."
Mr Trump, whose position on gun control has changed over the years, gave no further detail.
By James Cook, BBC, Las Vegas
The bereaved are beginning to tell their stories.
They speak of lives wasted, families broken, futures stolen.
This is a city in pain but it is also a city of heroes, bursting with tales of bravery and resourcefulness in saving lives.
There are the police officers who risked death on the 32nd floor to stop the shooting.
There are the music fans who shielded friends and loved ones from bullets, who comforted dying strangers and who commandeered trucks to get the wounded to hospital.
There are the surgeons who continue to labour in the operating theatres, saving lives, barely aware if it's day or night.
And there are the citizens of Las Vegas proving the selfish, greedy stereotype of their city wrong — queuing from before dawn to give blood, handing out cups of coffee and bagels for free, opening their doors to those most in need.
Above all else though there is grief. It is both personal and extensive.
The scale of the suffering inflicted here is difficult to comprehend and even harder to bear.
Paddock, a former accountant with a big gambling habit, lived in a community of senior citizens in the small town of Mesquite, north-east of Las Vegas.
He reportedly shared his house there with Danley. Initially police had said she was in Japan rather than the Philippines and discounted her involvement.
Nineteen firearms, some explosives and several thousand rounds of ammunition with electronic devices were found at the property.
Suspected gunman Stephen Paddock - undated image
Officers also found ammonium nitrate in Paddock's car - the chemical compound used in fertilisers can be used to make bombs such as that used in the 1995 Oklahoma City attack.
David Famiglietti of the New Frontier Armory told the BBC that Paddock had purchased firearms at his store in North Las Vegas in the spring of this year, meeting all state and federal requirements, including an FBI background check.
However, the shotgun and rifle Paddock bought would not have been "capable of what we've seen and heard in the video without modification", Mr Famiglietti said.
The fast shooting rate audible in recordings of Sunday night's attack indicates that Paddock may have modified his guns with legal accessories to make them fire at speeds approaching those of automatic weapons.
Despite the large cache of weapons found in the killer's home, his brother, Eric, is struggling to accept that he acted in this way. He said he was "in shock, horrified, completely dumbfounded".
So-called Islamic State claimed on Monday to be behind the attack, saying Paddock had converted to Islam some months ago. But the group provided no evidence for this and has made unsubstantiated claims in the past.
The FBI said it had found "no connection to an international terrorist organisation".
The final shows of the three-day Route 91 country music festival were in full swing when the gunman struck.
According to police, Paddock had booked into the hotel four days earlier, on 28 September, reportedly using some of Ms Danley's identity documents.