Gun stores nationwide are selling out of bump stocks, a device used by the Las Vegas shooter that allows a semiautomatic gun to fire as quickly as a machine gun.

Police said Stephen Paddock, the 64-year-old gunman, had outfitted 12 of his firearms with bump stocks, which he used to fire hundreds of rounds into a crowd of 22,000 concertgoers Sunday from the 32nd floor of the Mandalay Bay Resort and Casino. Hundreds were injured and at least 59 people were killed, including Paddock, who died from an apparent self-inflicted gunshot wound.

While some retailers, such as Walmart and Cabela’s, discontinued the sale of bump stocks following the shooting, others couldn’t keep up with the demand. At least six online gun retailers examined by Newsweek had sold out of the device this week.

Slide Fire, a Texas-based manufacturer of bump stocks, sold out of the devices within days of the mass shooting. The company posted a note to customers on its website:

“We have decided to temporarily suspend taking new orders in order to provide the best service with those already placed.”

Another Texas-based bump stock manufacturer, Bump Fire Systems, noted on its Facebook page on Tuesday that its website couldn’t handle the amount of interest it had received this week.

“Currently our servers are down due to high traffic volume,” read a post on Bump Fire Systems’ Facebook page. “Please be patient, our IT Dept is currently working on the issue as fast as possible.”

George Frey / Reuters A bump stock sold in Utah on Oct. 4, 2017.

Dozens of people commented on the post, leaving messages ranging from condemnation over the sales to desperate inquiries about when it would be possible to purchase the devices. Neither Bump Fire Systems nor Slide Fire immediately returned HuffPost’s requests for comment.

“Will I be able to order sometime soon?” one Facebook user asked. “I want to get one before there is a push to make them illegal.”

Jay Roberts, a 43-year-old municipal worker in Ohio, said he bought his first bump stock in 2012 because he wanted to try out a full automatic weapon, but “couldn’t afford the outrageous price” of one. He fired through two magazines using his new bump stock before putting it in his safe, he said, where he’s left it ever since.

“The bump stock is nothing more than a novelty item,” Roberts told HuffPost in an email on Thursday. “It is very impractical and would take quite a bit of training to be able to even remotely wield one as a viable weapon.”

“Also, you do not even need a bump stock to fire rapidly,” he said, noting that he ordered another one this week in case the government issues a ban against the device. “[A] simple YouTube search will show you that.”

Complete freedom comes with risks. Jay Roberts, 43-year-old bump stock owner

While fully automatic weapons are strictly regulated under federal law, bump stocks offer gun owners a relatively easy ― and cheap ― way to get around such restrictions. The devices, which could be purchased online for as little as $100, enable a user to fire hundreds of rounds per minute.

Slide Fire and Bump Fire Systems were uncertain they would be able to legally sell bump stocks when they first developed them. But in 2010, the Bureau of Alcohol, Tobacco, Firearms and Explosives, responding to an inquiry from Slide Fire, noted that bump stocks were not regulated under the Gun Control Act or the National Firearms Act.

Gun sales (and, in turn, gun stocks) typically rise after mass shootings, as many eager buyers worry the government will pass legislation that would significantly crack down on gun ownership and use. But lawmakers rarely do so, even when children are slaughtered at their elementary school or churchgoers are gunned down during Bible study.

Still, Sunday’s mass shooting ― the deadliest in modern U.S. history ― has renewed debate over gun control on Capitol Hill. Sen. Dianne Feinstein (D-Calif.), a longtime proponent of stricter gun control legislation, introduced a bill on Wednesday that would ban the sale and possession of bump stocks.

“The only reason to modify a gun is to kill as many people as possible in as short a time as possible,” Feinstein told reporters.

The only reason to modify a gun is to kill as many people as possible in as short a time as possible. Sen. Dianne Feinstein (D-Calif.)

The bill, titled the Automatic Gunfire Prevention Act, currently has 26 co-sponsors and would go into effect 180 days after its passage. Though zero Republican lawmakers have pledged their support, some have said they might be open to the idea of banning bump stocks.

“I’ll look at it for sure,” Sen. David Perdue (R-Ga.) said. “You can’t buy a chain-fed machine gun in the United States today. There’s a reason for that. And I want to make sure that nobody has access to that if that’s the law of the land.”

On Thursday, House Speaker Paul Ryan (R-Wis.) became the highest-ranking Republican to call for scrutiny of bump stocks.

“Look, I didn’t know what they were until this week, and I’m an avid sportsman, and so we are quickly coming up to speed with this,” Ryan said in an interview with MSNBC’s Hugh Hewitt. “So to turn a semiautomatic to fully automatic is something we have to look into.”

Even the National Rifle Association, the massive gun rights advocacy group that has spent millions of dollars lobbying against gun control legislation, places some restrictions on bump stocks at its own headquarters in Fairfax, Virginia.

The gun range there doesn’t allow the use of such devices, an NRA employee confirmed to HuffPost on Thursday. The NRA did not immediately answer HuffPost’s request for comment about why or when this rule was implemented.

Despite Sunday’s mass shooting and the unparalleled levels of gun violence in the U.S., many gun enthusiasts are none too pleased by the prospect of tighter gun laws. They claim that more gun restrictions likely wouldn’t have prevented Paddock’s attack.

Roberts said he believes automatic weapons should be available to anyone who “can complete a background check” and said it wouldn’t be the “American way” to shut down bump stock manufactures like Slide Fire just because some people feel they are “complicit” in mass shootings.

“The problem is the guy pulling the trigger,” Roberts said. “Back in the day we had mental hospitals, where people could get treatment. They are now turned loose on the street or in prisons because of the notion that inclusion in society is a better way. I don’t agree with that.”

“The problem with the animal in Vegas is that he didn’t show any signs [of mental illness], that the public knows of, so what do you do about that? I don’t have an answer,” Roberts added.

“Complete freedom comes with risks,” he concluded. “Risks I’m ok with.”

This story has been updated with a quote from Paul Ryan and information about the NRA’s restrictions on bump stocks at its gun range.