The man behind the worst mass shooting in modern US history had an arsenal of at least 42 guns, explosives and several thousand rounds of ammunition.

Officers recovered 19 firearms, explosives and ammo from Stephen Paddock's home in Mesquite, Nevada hours after discovering 23 guns in the Las Vegas hotel room from which he killed at least 59 concertgoers.

Earlier, police found several pounds of ammonium nitrate, a chemical used to make explosives, in the 64-year-old's car.

Some of the firearms recovered from his hotel room had scopes, while two were reportedly modified to make them fully automatic.

Las Vegas Police Department said officers were searching another home owned by Paddock in Reno, Nevada, adding that authorities were still unclear about the gunman's motive.

"I can't get into the mind of a psychopath at this point," sheriff Joe Lombardo said.

Detectives have described him as a "lone wolf" and dismissed speculation there were more assailants.

SWAT teams found the retired accountant dead in his room on the 32nd floor of the Mandalay Bay hotel.

"Act of pure evil"

Paddock's brother said he was "not an avid gun guy" and claimed he had become a multi-millionaire through real estate investments.

In a televised address, US President Donald Trump described the shooting as an "act of pure evil" but did not make reference to a growing row over Americans' right to bear arms.

White House press secretary Sarah Huckabee Sanders later told reporters that it was "premature" to discuss tighter gun regulations.

Side-stepping reporters' questions over the Las Vegas massacre, Ms Sanders said such debate was "premature" as the facts are not fully known.

Asked if the deadliest shooting in modern US history had prompted Mr Trump to consider tighter gun controls, Ms Sanders said: "Now is the time to unite as a country."

She added: "Today is a day of reflection, a day of mourning, a day of gratefulness for those that were saved.

"There will be time for that policy discussion to take place but that's not the place that we are in at the moment."

The Mandalay Bay hotel-casino is seen from a distance as Las Vegas Metro Police block off Las Vegas Blvd. the morning after a gunman fired on concertgoers | Image: Martin S. Fuentes/Zuma Press/PA Images

Pushed further, Ms Sanders described the president as a "strong supporter of the Second Amendment (right to bear arms)" - adding he did not want to push through laws that would not prevent mass shootings.

She said: "If you look to Chicago where you had over 4,000 victims of gun-related crimes last year, they have the strictest gun laws in the country.

"That certainly hasn't helped there, so when that time for those conversations to take place, we will look at things that can actually have a real impact."

Gun debate

The Las Vegas shooting has reignited debate over the ease of access to firearms in the US, with Hillary Clinton criticising the National Rifle Association (NRA) for backing legislation that would relax rules over the purchase of silencers.

Mrs Clinton tweeted: "Our grief isn't enough. We can and must put politics aside, stand up to the NRA, and work together to try to stop this from happening again."

Our grief isn't enough. We can and must put politics aside, stand up to the NRA, and work together to try to stop this from happening again.

— Hillary Clinton (@HillaryClinton) October 2, 2017

The NRA donated $30m (€25.6m) to Mr Trump's presidential campaign - and in April, the US leader told members they had "a true friend in the White House".

Asked about Mrs Clinton's remarks, Ms Sanders said it "isn't a time for us to go after individuals or organisations".

She added: "It's very easy for Mrs Clinton to criticise and come out but I think we need to remember the only person with blood on their hands is... the shooter."

Mr Trump will visit Las Vegas on Wednesday to "grieve with the friends and family of the victims, offer his support to those recovering from wounds and thank courageous first responders", Ms Sanders added.

City officials have made an urgent appeal for blood donors as at least 527 people who were injured in the shooting are treated in hospitals across Nevada.

Some of those wounded were hit by shrapnel, while others were trampled on as hundreds fled the concert in panic.

After visiting a hospital in Las Vegas, US Congressman Ruben Kihuen said: "Literally, every single bed was being used, every single hallway was being used. Every single person there was trying to save a life."