Senate Democrats cited mass shootings in Las Vegas and Newtown, Connecticut, before filing legislation Wednesday to expand background checks on those purchasing weapons at gun shows.

Sen. Catherine Cortez Masto, D-Nev., speaks at a town hall meeting Tuesday, April 18, 2017, in Las Vegas. (AP Photo/John Locher)

Sen. Catherine Cortez Masto, D-Nev., surrounded by gun control supporters during news conference at the U.S. Capitol for a bill to expand background checks. (Gary Martin/Las Vegas Review-Journal)

WASHINGTON — Senate Democrats cited mass shootings in Las Vegas and Newtown, Connecticut, before filing legislation Wednesday to expand background checks on those purchasing weapons at gun shows.

The legislation was filed a day after the FBI released more than 1,500 pages of documents that were part of the investigation into the 2012 Sandy Hook Elementary School shooting that led to the death of 20 first-graders and six educators.

Las Vegas was the scene of the most deadly mass shooting in recent American history on Oct. 1 when Stephen Paddock, 64, used multiple semi-automatic weapons to shoot from a 32nd floor window into a country music concert below.

The attack left 58 dead and hundreds injured.

Even though Paddock passed background checks to purchase rifles used in the attack, lawmakers said expanding the law to close a loophole on weapons purchases at gun shows, or through private sales, was a common sense measure.

“We must work to keep gun out of the hands of the seriously mentally ill, people with a history of violence, criminals and terrorists,” Sen. Catherine Cortez Masto, D-Nev., told a Capitol Hill news conference.

She said the measure is needed to “stop the violence that has become too common in big cities and small towns across America.”

“It’s about saving lives in the future,” Cortez Masto said.

The bill was introduced by Sen. Chris Murphy, D-Conn., who worked with Sen. Dick Blumenthal, D-Conn., and Sen. Dick Durbin, D-Ill., on the legislation after the Newtown tragedy.

Current background checks prevented 100,000 people with criminal or mental history from buying weapons, Murphy said.

The FBI documents released this week showed that Adam Lanza, 20, suffered from Asperger’s syndrome and was obsessed with firearms, death and mass shootings. Lanza, who never purchased guns, shot his mother Dec. 14, 2012 before going to school where he murdered young children before taking his own life.

In Nevada, Paddock amassed an arsenal of weapons. But law enforcement said he had no criminal or mental history that would have alerted officials of a potential threat. That investigation is still ongoing.

People who have lost loved ones to gun violence attended the news conference at the Capitol, and told personal stories about how a federal law could prevent a future death.

A bill to expand background checks in 2013, following the Newtown mass shooting, failed to advance in Congress. In Nevada, a measure to require background checks on private-party gun transfers was narrowly approved by voters in 2016, but it has been deemed unenforceable.

The National Rifle Association has opposed federal efforts to expand background checks, saying additional checks would not stop criminals from obtaining weapons.

Legislation introduced after the Las Vegas shooting also faces hurdles in the House and Senate, where Republicans control both chambers.

After the Las Vegas shooting, some lawmakers sponsored legislation to ban “bump stocks,” devices used by Paddock to increase the rate of fire of semi-automatic rifles.

The NRA wants the Trump administration to review current law on the devices to see if regulations should be tightened, not banned outright with legislation.

Rep. Dina Titus, D-Nev., urged Congress again Wednesday to address the legislation.

“Congressional Republicans and the NRA signaled support of action on bump stocks in the wake of the 1 October tragedy,” Titus said. “But since then, their hopeful and sympathetic tone has morphed into radio silence.

“We cannot ignore the fact that if we don’t act soon, we risk jeopardizing more innocent lives,” Titus said in a speech from the House floor.

Following her speech, Titus read the names of all 58 victims of the Las Vegas shooting into the Congressional Record.

Contact Gary Martin at gmartin@reviewjournal.com or 202-662-7390. Follow @garymartindc on Twitter.