Las Vegas shooting: How Stephen Paddock got guns into Mandalay Bay

The broken window seen at the Mandalay Bay resort and casino where Stephen Paddock opened fired on 22,000 concert-goers. Photos / AP

The man behind the deadliest shooting in US history had ample time to smuggle his weapons arsenal into his hotel room, ready to carry out his massacre.

A former Las Vegas Metropolitan Police Department officer said Stephen Paddock had been staying at the Mandalay Bay hotel-casino for three days before the shooting took place.

Randy Sutton, who spent 24 years with the police force, told CBS This Morning the amount of firepower in the room indicated it wasn't all brought up in just one trip.

"And he certainly didn't have bellmen bring that up," he said.

"So having been there for three days, he had the time to bring that up probably in either luggage or a golf bag or something of that nature."

He said Paddock managed to keep his weapons hidden from hotel staff who would have come into the room.

Paddock had a stash of weapons in room 135 on the 32nd floor from where he shot 59 people dead and injured 527.

Assistant Clark County Sheriff Todd Fasulo said officers found 23 firearms in the hotel room of and 19 firearms at Paddock's home in Mesquite, Nevada.

Most of those found in the hotel room are military-style rifles, while two were modified with a "bump stock" device.

This device allows the shooter to fire off rounds quickly without converting it to a fully automatic weapon.

A semiautomatic weapon requires one trigger pull for each round fired.

With a fully automatic firearm, one trigger pull can unleash continuous rounds until the magazine is empty.

The device basically replaces the gun's shoulder rest.

By holding the pistol grip with one hand and pushing forward on the barrel with the other, the shooter's finger comes in contact with the trigger. The recoil causes the gun to buck back and forth, "bumping" the trigger.

Technically, that means the finger is pulling the trigger for each round fired, keeping the weapon a legal semiautomatic.

Clark County Sheriff Joseph Lombardo said police also found 18 firearms, explosives and several thousand rounds of ammunition at Paddock's home in Mesquite, Nevada.

He said investigators found several pounds of an explosive called tannerite in the gunman's home, as well as ammonia nitrate, a type of fertiliser, in his car.

Police are continuing to investigate the motives behind the shooting.

"I can't get into the mind of a psychopath," Sheriff Lombardo told a news conference.

He said the shooter took his own life when authorities entered the room.

DEADLY RAMPAGE

A night time view of the scene of the mass shooting, bottom right, on the Las Vegas Strip. Photo / AP

According to the New York Times, an AR-15-style assault rifle was among the weapons found in room 135.

However, it wasn't clear if this was used to smash open the windows of the room, where Paddock had been staying since September 28.

Paddock had purchased several firearms, many in California, however they didn't appear to be among those found in the hotel room.

A .223 caliber gun and a .308 caliber gun were among the weapons found, according to CNN.

Police have not yet confirmed the weapon Paddock used in the massacre, but said he smashed the hotel windows with a hammer-like object to get a clear shot at the 22,000-strong crowd.

Two devices were attached to the stocks of semiautomatic guns to allow fully automatic gunfire, according to the Associated Press.

The sheriff said Paddock checked into his room at the Mandalay last Thursday and brought the weapons to the hotel "on his own", National Public Radio reported.

However police did not know what he had been doing in the days leading up to the shooting.

Hotel staff had also been into the room but didn't notice anything unusual.

'NO RED FLAGS'

Police tape blocks off the home of Stephen Craig Paddock. Photo / AP

Meanwhile the owner of a Utah gun store said Paddock visited the store several times this year and bought a shotgun after passing a federal gun background check.

Dixie GunWorx owner Chris Michel said Paddock was new to the area and visiting local gun shops.

Paddock bought the shotgun in February and last visited the store in St George, Utah, in the spring.

Michael told the AP he spoke with Paddock to make sure there were no signs that he should not be allowed to buy a gun.

"There were no red flags," he said. "I had no idea he would be capable of this."

Another gun shop owner Christopher Sullivan told the New York Times Paddock had purchased a handgun and two rifles from his shop in the past year.

Sullivan, the general manager of Guns & Guitars in Mesquite, said the purchases met legal and routine federal screening requirements.

He said Paddock seemed like a nice, normal guy.

"As for what goes on in a person's mind, I couldn't tell you," Sullivan said.

"I know nothing about him personally."

It comes as Paddock's own brother Eric said he had no idea of the amount of weapons his sibling had.

He told the Washington Posthis brother owned a couple of handguns but was had no idea he had a rapid-fire weapon like the one believed to have been used in the shooting.

He said his brother didn't hunt and hardly used his guns.

Eric Paddock also said he and his family were dumbfounded and at a loss to explain the reasons behind the tragedy.

Reed Broschart, center, hugs his girlfriend Aria James on the Las Vegas Strip in the aftermath of a mass shooting at the concert. Photo / AP

- with the Associated Press