A Texas woman who was injured in the mass shooting in Las Vegas filed a lawsuit on Tuesday against MGM Resorts International, the festival organiser and a company that makes "bump stocks".

Paige Gasper, 21, and her friends were enjoying the Route 91 Harvest festival on October 1 when gunman Stephen Paddock fired into the crowd, killing 58 concertgoers and injuring 489 others, according to Daily Mail.

As Gasper tried to run to safety, a bullet pierced her right underarm, shattering her ribs and lacerating her liver, according to the lawsuit.

Gasper was rescued by a good Samaritan who helped her take cover behind a dumpster before leading her to a truck that took her to Spring Valley Hospital Medical Center, according to the Las Vegas Review Journal.

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She underwent multiple surgeries and is recovering in California, where she also attends Sonoma State University where she studies psychology.

The Mandalay Bay hotel, where Paddock staged his deadly attack from his suite, is owned by MGM Resorts International.

Along with MGM Resorts, the complaint filed in Clark County District Court names Paddock's estate, Live Nation Entertainment Inc, Mandalay Corp and Slide Fire Solutions LP, which makes bump stock devices.

Police said that Paddock used bump stocks to turn semi-automatic weapons into fully automatic guns.

The National Rifle Association (NRA) recently called for new regulations of "bump stock" devices that allow gun-owners to convert semi-automatic arms into a rapid-fire arms akin to an automatic.

On Thursday, the group issued its first statement since the Las Vegas massacre - a potential game-changer after Democrats and a series of Republican lawmakers have proposed taking action on the issue.

MGM Resorts International owns the Mandalay Bay Resort and Casino. Photo / Supplied
MGM Resorts International owns the Mandalay Bay Resort and Casino. Photo / Supplied

"The NRA believes that devices designed to allow semi-automatic rifles to function like fully-automatic rifles should be subject to additional regulations," NRA CEO Wayne LaPierre and the group's top lobbyist Chris Cox said in a joint statement.

Texas attorney, Michelle Tuegel, who is representing Gasper said the lawsuit focuses on the companies "who have a responsibility to keep the people who are on their properties at their events safe".

Tuegel also referred to Paddock installing a peephole in his suite and asked: "How did the hotel not know about that? Why wasn't that a red flag?"

"We are a simple and humble family, and money is not the driving force of us asking us to be heard," Gasper's mother, Heather Selkin, said through tears during a press conference.

"When we buy a ticket to an event, we need to know that our safety is considered," she added.

Gasper's lawyers said the lawsuit focuses in part on the timeline for the shooting, which has raised questions in the last few days.

Chad Pinkerton, who is also representing Gasper, said the six minutes between when authorities say security guard Jesus Campos was shot and when Paddock sprayed bullets into the crowd "was crucial".

"Those people that were killed and injured deserved to have those six minutes to protect them," he added.

Gasper's lawyers did not give a specific amount of damages sought in the case.

MGM Resorts recently questioned the accuracy of the most recent police timeline before the shooting.

On Monday Las Vegas police said Campos was shot six minutes before Paddock committed the mass murder - a revision to the original police timeline that raises huge questions.

The new timeline raises questions about what the killer had been planning before Campos disturbed him, and why police did not arrive sooner.

And one of the groups raising those questions is MGM - owner of the Mandalay Bay Hotel - which issued a statement saying that timeline "may not be accurate".

Las Vegas gunman Stephen Paddock. Photo / AP
Las Vegas gunman Stephen Paddock. Photo / AP

It is unclear what she means by this or what has prompted the company to make this allegation.

"This remains an ongoing investigation with a lot of moving parts," MGM Resorts spokesperson Debra DeShong told the New York Post.

"As evidenced by law enforcement briefings over the past week, many facts are still unverified and continue to change as events are under review. We cannot be certain about the most recent timeline that has been communicated publicly, and we believe what is currently being expressed may not be accurate."

DeShong went on to say: "We understand the public's desire for information and the importance of getting our community and the public at large the information they deserve, and we are doing everything we can to support law enforcement's efforts to do so.

"Therefore, it is not appropriate for us to comment further at this time on what remains an open matter for law enforcement."

This comes two days after Las Vegas Sheriff Joseph Lombardo said that Campos had approached the room on the 32nd floor of the Mandalay Bay hotel not because of gunfire, but because of an open-door alarm that had gone off nearby.

Paddock then apparently saw him on the video cameras he'd rigged up in the hall and opened fire on him. That occurred at 9.59pm. Lombardo said last week that Paddock fired more than 200 rounds in that encounter.

Campos "immediately, upon being injured, notified security of his situation," Lombardo said.

Paddock then turned his gun on the 22,000 revelers at the Route 91 Harvest country music festival five minutes later, per the original timeline of 10.05pm, Lombardo said.

That contradicts what had been said last Wednesday by Lombardo, who claimed that Campos had approached Paddock while he was firing at around 10.15pm.

Paddock turned his gun on Campos, before stopping firing altogether, he said.

Police arrived just minutes later to a silent hallway, Lombardo claimed - at which point they assumed Paddock was barricaded in and no longer a threat to revelers.

With the hall silent, they - and Campos, who was injured but wanted to help - were free to evacuate the rest of the rooms leading up to Paddock, he said.

That was used as an excuse by Lombardo to explain the delayed response - arguing that even if Campos had not been there, other officers would have disrupted the massacre themselves.

Police hiding behind a cop car as a gunman opens fire on festival-goers. Photo / Getty Images
Police hiding behind a cop car as a gunman opens fire on festival-goers. Photo / Getty Images

But in the new timeline that excuse no longer works; Campos lay wounded for six minutes before Paddock started firing, police now say.

It also means that Paddock fired for ten minutes on the crowd before stopping abruptly - for reasons that now have police baffled.

Of course, that in turn leaves a 16-minute window in which Paddock was left undisturbed while hundreds were injured and dozens died, and a 19-minute window between Campos being struck and cops arriving.

Speaking on Monday, Lombardo seemed to want to shift some of the blame for the discrepancy onto Campos.

"As you might imagine, Mr Campos was not only injured when he was fired upon as he [checked on] the door alarm down the hall... he was also extremely shaken up about what had happened to him," Lombardo said.

"He was able to confirm to us exactly what he heard and saw in the moments before he was shot."

He later added: "In [the presses] zest for information, in my zest to insure the public safety, in the calming their minds, some things are going to change. They are minute changes... [what was said before was] not completely inaccurate."

It's not clear which door Campos heard the alarm at, but previously Lombardo had said that SWAT teams approaching Paddock's room from the stairwell next to it had found the stairwell's door tampered with and sealed.

Paddock had drilled holes into it and bolted it with a metal bar to stop it being opened, police said.

Lombardo also said on Monday that Campos heard Paddock drilling inside the room as he approached, possibly to install a camera or a gun.

That drill work was to the wall next to the doorway and not finished, the sheriff added.

When asked if he believed Paddock had stepped up the timeline and opened fire early because of the disruption, Lombardo declined to comment.

He also said that while he waited for police to arrive, Campos stopped a maintenance worker from entering the 32nd floor.

Inside the gunman's hotel room. Photo / Twitter
Inside the gunman's hotel room. Photo / Twitter

Also on Monday, Lombardo suggested that Paddock had planned to blow up nearby jet fuel tankers in the hopes of creating a distraction to escape.

Lombardo had previously said he believed Paddock intended to flee the scene of the massacre. When asked again, he said that "conversation" was ongoing.

Although it wasn't a department-wide belief, he said, he was "comfortable" in saying that Paddock had hoped to flee.

"The suspect, we know he attempted to shoot at the fuel tanks, we know he had some personal protection equipment in the room, we know the car in the parking garage contained binary explosives," he said.

"I would be comfortable saying, which I believe, that depending on the splash [damage caused by the exploding tanks] he made in the shooting, would it have enabled the first responders to direct their attention to other locations, to help Mr Paddock leave the hotel."

Paddock is now confirmed to have checked into the hotel on the 25th, and police are now trying to work out what he did between then and the 28th, Lombardo said.

It's not believed he was staying in the hotel at that time.

He added that investigators had documented more than 200 instances of Paddock's movements throughout Las Vegas in the lead-up to the shooting.

At none of those points did police find any indication he was seen with anyone else, Lombardo said, reiterating that Paddock had no ties with "any known terrorist groups or ideologies".