A suspected "lone wolf" gunman sparked the deadliest mass shooting in modern US history when he opened fire on a crowd of concertgoers from the 32nd floor of a Las Vegas hotel, killing at least 58 people and injuring hundreds more, police said.

More than 22,000 people were attending the performance by country music star Jason Aldean Sunday night at the Route 91 Harvest Festival when the gunman hammered out a window at the Mandalay Bay Hotel and Casino and began firing with a cache of weapons.

Authorities who stormed the suspect's room found that he had killed himself.

THE INVESTIGATION

Officials say the suspected gunman, Stephen Craig Paddock, a 64-year-old retiree from Mesquite, Nevada, wasn't on the radar of law enforcement. They think he acted alone but want to talk with his 62-year-old roommate.

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There also were no known links to any international terror organisations, officials said, despite a claim of responsibility by the Islamic State group.

The sheriff's department is leading the investigation, and Attorney General Jeff Sessions ordered support from the FBI and other federal agencies.

Read more:
How cops tracked killer to room

A woman sits on a curb at the scene of the shooting. Photo / AP
A woman sits on a curb at the scene of the shooting. Photo / AP

THE VICTIMS

At least 515 people were injured in the attack, along with the 58 confirmed dead.

Among the confirmed fatalities was Sonny Melton, a registered nurse. His wife, Dr. Heather Melton, an orthopedic surgeon who was with him when shots were fire, survived.

Heather Melton told WZTV in Nashville that her husband "saved my life and lost his." She says her husband was the most kind-hearted, loving man she ever met.

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'I felt him get shot in the back'

THE GUNMAN

Paddock was living in Mesquite, Nevada, and authorities say he previously lived in the Dallas suburb of Mesquite, Texas, from 2004 to 2012, and possibly longer.

Lt. Brian Parish says property records show Paddock owned at least three rental properties.

Officers searched the Nevada home on Monday, and authorities there and in Texas indicated there wasn't law enforcement contact with him.

Paddock's brother, Eric Paddock, who lives in Florida, told the Orlando Sentinel: "We are completely dumbfounded. We can't understand what happened."

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Face of a killer

PRESIDENT'S RESPONSE

President Donald Trump called the shooting an "act of pure evil" during an address from the White House.

He said he would be going to Las Vegas on Wednesday "on a very, very sad moment for me ... for everybody no matter where you are, no matter what your thought process."

Trump and first lady Melania Trump were leading a moment of silence Monday afternoon at the White House South Lawn to honor the victims. He also spoke by phone with British Prime Minister Theresa May about the shooting.

COUNTRY MUSIC REACTION

Stars from the world of country music sent out their condolences to the victims of the tragedy.

Luke Combs, who performed earlier in the night, said on Instagram: "I can't help but hurt for all the people who weren't as fortunate and the pain their loved ones must feel."

Carrie Underwood posted on Twitter : "Woke up to such horrible news. We are praying for the victims and their families. May the Lord bring some comfort to them."

"Stilled and speechless," Keith Urban tweeted. "Our hearts and prayers are with everyone involved and affected."