Some members of congressional Republican leadership have expressed a willingness to explore legislation banning bump stocks, the attachment that the Las Vegas shooter used to effectively make semiautomatic rifles fire at the rate of automatic ones.

Investigators in Las Vegas found that 64-year-old Stephen Paddock, who killed at least 59 people and injured more than 520 in a mass shooting there late Sunday night, had 12 rifles fitted with bump stocks in the 32nd-floor hotel room from which he fired upon a crowd outside the Mandalay Bay Resort and Casino.

Senate Majority Whip John Cornyn of Texas indicated he might consider a bill from Democratic Sen. Dianne Feinstein of California banning bump stocks.

“If somebody can essentially convert a semiautomatic 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 told reporters Wednesday.

Watch Trump’s Full Remarks on the Las Vegas Massacre

“I own a lot of guns and as a hunter and sportsman, I think that’s our right as Americans, but I don’t understand the use of this bump stock and that’s another reason to have a hearing,” the Texas Republican added.

Semiautomatic rifles require the shooter to manually pull the trigger to fire each round. A bump stock attachment modifies the gun’s mechanics, allowing shooters to empty magazines in a matter of seconds.

The government approved the selling of the devices in 2010 after concluding they did not violate federal law.

Cornyn said Senate Judiciary Chairman Charles E. Grassley was interested in holding a hearing on the matter.

Other important GOP senators revealed Wednesday that they have people in their office researching bump stocks and potential curbs to their sale.

“I’m interested in finding out more about bump stocks and I’ve got my staff looking into that,” Sen. John Thune of South Dakota said. “I know there are other members interested in finding out more about it as well.”

Cornyn and Thune’s comments veer from the GOP norm of shooting down most forms of firearm regulation before legislation gains momentum.

Senate Majority Leader Mitch McConnell and House Speaker Paul D. Ryan have indicated that Feinstein’s proposal is not at the top of the legislative agenda.

Both have said the shooting’s immediate aftermath is not the right time to consider legislation since emotions are raw and investigators have still not uncovered all the facts.

President Donald Trump echoed McConnell and Ryan on Wednesday in Las Vegas.

“We’re not going to talk about that today,” the president said, when asked about gun issues.