WASHINGTON, D.C. – Both of Vermont’s Senators have signed on to a bill which would ban devices for making semi-automatic guns automatic.

Twelve such devices were found in the hotel room of Stephen Paddock. Paddock killed 59 people and injured more than 500 in approximately nine minutes of gunfire, before killing himself.

The Automatic Gun Fire Prevention Act was proposed by Sens. Dianne Feinstein (D-Calif.) and Richard Blumenthal (D-Conn.). Feinstein introduced another version of the bill following the killing of 20 first graders and six adults at the Sandy Hook Elementary School in 2012. The Senate never voted on the bill.

Semi-automatic rifles typically have a rate of fire between 45 and 60 rounds per minute. A bump stock, or other similar device, increases the semi-automatic rifle’s rate of fire to between 400 and 800 rounds per minute.

Speaking at a press conference with Feinstein and Blumenthal on Wednesday, Sen. Bernie Sanders, I-Vt., emphasized the speed with which Paddock was able to kill and injure so many. “The reason he was able to accomplish so much destruction, so much killing and wounding, in such a short period of time, was because he used a simple device to convert his semi-automatic rifles into fully automatic rifles,” said Sanders.

“We agreed as a nation many decades ago to ban fully automatic weapons. Unfortunately, these so-called ‘bump stocks’ provide an effective workaround to convert a legal weapon into an illegal weapon. In other words, if we want to enforce and honor the law passed in 1986, it is imperative that we pass Sen. Feinstein’s legislation,” Sanders continued.

The 1986 Firearm Owners Protection Act made it illegal in the U.S. to own, sell or transfer automatic weapons, although it left a loophole for already existing automatic weapons.

“We’ve now witnessed the deadliest mass shooting in U.S. history, which saw nearly 600 people killed or injured. An American concert venue has now become a battlefield. We must stop this now,” Feinstein said. “Automatic weapons have been illegal for more than 30 years, but there’s a loophole in the law that can be exploited to allow killers to fire at rates of between 400 and 800 rounds-per-minute. The only reason to fire so many rounds so fast is to kill large numbers of people. No one should be able to easily and cheaply modify legal weapons into what are essentially machine guns.”

“While it is too late for the victims in Las Vegas, and the victims in Newtown, and the victims in Charleston and the other terrible shootings that we have seen, it is not too late to prevent the next set of innocent Americans from becoming victims,” Sanders said. “Now is the time to save lives in this country. Now is the time to pass this legislation.”

The bill would ban the sale, transfer, importation, manufacture or possession of bump stocks, trigger cranks and similar accessories that accelerate a semi-automatic rifle’s rate of fire.

The bill makes clear that its intent is to target only those accessories that increase a semi-automatic rifle’s rate of fire. Legitimate accessories used by hunters would be exempt. The bill also contains exceptions for lawful possession of these devices by law enforcement and the government.

In addition to Sens. Feinstein, Sanders and Blumenthal, cosponsors include Sens. Chuck Schumer (D-N.Y.), Dick Durbin (D-Ill.), Chris Murphy (D-Conn.), Patrick Leahy (D-Vt.), Chris Van Hollen (D-Md.), Ed Markey (D-Mass.), Kirsten Gillibrand (D-N.Y.), Amy Klobuchar (D-Minn.), Bob Casey (D-Pa.), Jack Reed (D-R.I.), Maggie Hassan (D-N.H.), Jeff Merkley (D-Ore.), Tom Carper (D-Del.), Cory Booker (D-N.J.), Kamala Harris (D-Calif.), Al Franken (D-Minn.), Sheldon Whitehouse (D-R.I.), Elizabeth Warren (D-Mass.), Mazie Hirono (D-Hawaii), Ben Cardin (D-Md.), Chris Coons (D-Del.) and Maria Cantwell (D-Wash.).

As of press time, no Republican members of Congress had announced support for the bill.

Some Republican senators, including Sen. John Cornyn of Texas indicated a willingness to give the bill a hearing. “If somebody can essentially convert a semi-automatic weapon by buying one of these and utilizing it and cause the kind of mayhem and mass casualties that we saw in Las Vegas, that’s something of obvious concern that we ought to explore,” Cornyn said.

Senate leader Mitch McConnell, R-Ky., refused to answer questions about Feinstein’s bill, saying now was not the time to discuss it.

House Speaker Paul Ryan, R-Wis., took a different tact, stating, “What I don’t think you want your government to do is to lurch toward reactions before even having all the facts. Bad people are going to do bad things.”

The Associated Press contributed to this report.