A Calgary woman who was eating dinner in a Las Vegas restaurant when a gunman opened fire on concertgoers, killing dozens of people, says she and her friends spent the next several hours huddled in a nearby mall as security and police tried to keep people safe.

The death toll has reached 59, with more than 500 people listed as wounded, in what officials are describing as the deadliest mass shooting in modern U.S. history.

A gunman on the 32nd floor of the Mandalay Bay Resort and Casino fired down on the crowd of tens of thousands of people assembled across the street for the Route 91 Harvest Music Festival, at an outdoor area known as Las Vegas Village. 

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Jacqueline Hoare was having dinner down the strip from her hotel when the shooting happened. (Facebook)

Jacqueline Hoare and her friends are staying at a hotel just up the strip from the Mandalay Bay, but she and her friends had walked about 15 minutes farther up the boulevard to have dinner.

When the shooting began, staff at the restaurant asked the guests to move inside. 

"It was brutal. Not really knowing and understanding the depth of what had happened," she said.

Hoare's friends, Lesley Plumley and Lynette MacDonald, said there was an atmosphere of confusion as the situation unfolded.

"We just didn't know what to do and it was just absolutely chaotic, in my opinion," said Plumley.

"Nobody really knew what was happening," said MacDonald. "Just that feeling of kind of being so helpless, and nowhere to go." 

Eventually, all the diners were told to go inside an adjacent mall. MacDonald said they were able to piece together what was happening by looking at Twitter feeds.

"At one point — we had sort of various situations of lockdown — at one point, we were sitting on a floor of a sporting goods store, kind of hunkered down under the clothing racks in the dark, and they'd closed the doors and locked the doors."

For the next several hours, Hoare said she and dozens of other people were kept in the mall as police and security officers responded to the attack and locked down all the hotels and the surrounding area.

"It was frightening, because we had only heard about the Edmonton situation, because we were flying to Las Vegas yesterday morning when that all came out," Hoare said.

"And then, to have something happen here … we had no idea of how tragic it was.

It's absolutely devastating."

Hoare said she wasn't able to get back to her hotel room until about 3:45 a.m. People from the music festival and from the Mandalay Bay resort were sleeping on the couches and floors at Hoare's hotel, still unable to return to their rooms.

"It puts so many things into perspective when you walk in and see that," said Plumley.

"You're happy you're safe, but you think, just across the street, there's so many people that were hurt and so many families affected by this. It's a surreal feeling."

Authorities have identified the person believed to be the gunman as Stephen Paddock, 64.

Officers confronted Paddock on the 32nd floor of the Mandalay Bay hotel. There are reports he killed himself before police could arrest him.

Westjet and Air Canada are waiving cancellation fees for people who had booked to go to Las Vegas.

Westjet says anyone can cancel between today and Wednesday without penalty.

Air Canada's policy is in effect until next Monday.

Both airlines are asking people who are travelling to Las Vegas this week to check whether their flights are on schedule​.