LAS VEGAS (CN) – Three people who attended the country music festival where a gunman massacred 58 people Oct. 1 have filed a class action against the maker of bump stock, an attachment used by the gunman to modify his semi-automatic rifles to fire at almost the same rate as automatics.

Devon Prescott filed the class action in Clark County, Nevada, court on behalf of all people who attended the Route 91 Harvest Music Festival near the Mandalay Bay Hotel, where Stephen Paddock rained gunfire onto the crowd attending the three-day event.

The putative class is represented by Robert Eglet and three others at Eglet Prince in Las Vegas, and by Jonathan Lowy of the Brady Center to Prevent Gun Violence in Washington. The gun control group is expected to announce the filing with the law firm at a Tuesday morning press conference in Las Vegas.

“The people who attended the concert have suffered so much already,” the firm and Brady Center said in joint statement. “The physical injuries are staggering, and we know the emotional injuries can be equally severe and long term. Brady has decades of experience supporting the victims of gun violence and has been the only organization in the nation focused on seeking justice for them in the courts.”

Prescott and two others name the maker of the bump stock device, Slide Fire Solutions of Moran, Texas, and other unidentified manufacturers. They claim Slide Fire markets the product under the guise that it helps gun owners who suffer from a lack of mobility in their hands. But bump fire stock inventor Jeremiah Cottle has stated the attachment was for “‘people like me, [who] love full auto,’” a statement that betrays the actual purpose of the product – to convert rifles into fully automatic firearms, according to the complaint.

Paddock fired at concertgoers from the 32nd floor of the Mandalay Bay Hotel on the night of Sunday, Oct. 1. The massacre is the worst mass shooting in modern U.S. history, killing 58 and injuring nearly 500.

Authorities say the 64-year-old gunman stashed more than dozen rifles and hundreds of rounds of ammunition in his hotel room. He rained gunfire on thousands of panicked concertgoers over 11 minutes.

Investigators found Paddock dead in his hotel room from a self-inflicted gunshot wound.

The Oct. 6 lawsuit says the class does not “challenge the right of law-abiding citizens to bear arms” but says that Slide Fire negligently sells bump stock to gun owners to avoid state and federal laws banning the use of military-style automatic weapons.

“Paddock could not have injured so many people without a bump stock. Paddock may not have launched his military-style assault without a bump stock. There are people who were killed, injured, and suffered emotional distress who would not have been if Paddock had not possessed a bump stock,” the 30-page filing states.

The National Firearms Act regulates the sale of fully automatic weapons so that members of the public cannot obtain them, according to the Brady Center.

Slide Fire grossed more than $10 million from the sales of bump stocks in 2010 and sold bump stock models for between $100 and $400, according to the lawsuit. The company has suspended the sale of the devices through its website, according to the Brady Center, and disabled a feature that allowed buyers to locate dealers through the site.

In a rare display of bipartisanship on the issue of gun violence, both Democrats and Republicans voiced support for a ban on a device. The powerful gun lobby National Rifle Association has said the Federal Bureau of Alcohol, Tobacco, Firearms and Explosives should take a closer look at the products but has also said it would challenge a complete ban.

The lawsuit seeks the creation of a court-supervised medical and psychological monitoring program for the class of plaintiffs, as well as punitive damages, attorney fees, and costs.

Slide Fire Solutions and Cottle did not respond to requests for comment. On Monday, Courthouse News was unable to leave a voicemail because the company’s inbox was full.